• This is a reasonable system for 2014, and a system that should last years with good care, but if you're looking at this in 2017 or later there are probably new options available for many of these components.
• This is appropriate for most halls, including something the size of the Concord Scout House, but a really big hall like Glen Echo will need something more powerful.
• I'm using Amazon links so you can see pictures and competitive prices, but of course that doesn't mean you have to buy from them.
• This is the system I would buy for a dance group, but people are going to disagree about various aspects. If there are bits you would do differently, let me know!

Mixer: Mackie ProFX16 ($500)

The world is switching to digital mixing and I love my 1818 VSL, but digital mixers are more complex and inconsistent. For a contra dance organization where a board is going to be used by lots of different people of varying skill levels a standard analog board is a better choice. You want six xlr inputs at a minimum, eight is good, a few more is better. If this board is too expensive you can get good used boards pretty cheap; I like the 8-xlr Spirit Folios.

These days most musicians will expect to be able to get phantom power from the board. This mixer does have phantom power, but it's all-or-nothing. Unfortunately you don't tend to get individually switchable phantom power until you get up to pretty expensive board.

Warning: mixers are generally sold as "N-channel" but in a contra dance context what you generally care about is the number of xlr inputs. Count them!

Mains: Two QSC K10s ($750 x2)

The K10 is an excellent speaker. It sounds very good, has a strong low end, and doesn't need an external amplifier. It has built-in tilters that let it angle down 7.5 degrees to decrease the amount of sound reflected off the ceiling. They also make a 12" version, the K12, but that's heavier and it's not necessary for most contra dance bands.

The Yamaha DXR10 ($600) is mostly a clone of the K10, and is a bit cheaper but without as good bass. If you have a small hall you might get just one K10 and set it up in the center of the stage instead of having two on the sides. This gives a very clear sound, but gets in the way a bit and can be too loud close to the speaker.

Monitors: Three srm150s ($250 x3)

For small bands personal "hotspot" monitors are great. You can point the monitor right at the musician's head, and can keep stage volumes down. Most mixers have at least two monitor outputs, so you can run at least two monitor mixes (ex: one for fiddle and mandolin, another for piano).

If you're going to get in a lot of bands with more than four musicians, though, a pair of larger monitors on the floor is generally better because it keeps clutter down. I would probably get another pair of the speakers you're getting for the mains: this gives you flexibility and simplicity.

The other main advantage of floor monitors is sound quality: the smaller monitors generally don't do much to reproduce the bass frequencies of a piano, guitar, or double bass. On the other hand, personal monitors can sound a bit more clear if you have them aimed well, and they generally have convenient volume controls where individual musicians can turn their monitor up and down to get their level exactly where they want it.

(For a little more on this, see the "update on monitoring" section of Bob Mills' excellent "All Mixed Up".)

Mics: Four sm58s ($100 x4)

The sm58 is a very versatile mic, and sounds pretty good with most instruments and voices. It's pretty sturdy, and doesn't need phantom power. If you want you could instead get a mix of sm58s and sm57s, but they cost the same and the sm58 has a windscreen, so I like the simplicity of just going with one kind of mic. (These come with their own mic clips.)

Many musicians these days will bring their own mic, especially fiddle players, so you'll rarely even need four. If you want to have a mic on hand for fiddle players to use, consider the AT PRO-35 ($100).

In general if the caller wants a wireless mic they'll bring one, but it's starting to become common and maybe even expected that dances will provide one. Wired mics tend to sound better, have less that can go wrong, and introduce less delay into the setup, so a wireless really only makes sense if people are going to take advantage of that ability.

Talking to bands and callers in advance of a gig is really useful here. Find out what they need, what they're bringing, and if there's extra gear you need like a DI box see whether they can bring it or if there's someone you can borrow one from.

Mains Stands: Two Ultimate Support TS88 ($110 x2)

Ultimate Support makes good stands, and the TS88 is a nice simple stand that's very tall. Getting the speakers nice and high over the dancers and angled down allows you to minimize reflected sound and keep a more even volume through the hall.

Monitor Stands: Three Short Stands ($13 x3)

The srm150s come with little adapters that twist onto standard mic stand mounts. If instead you decided to get floor monitors you don't need monitor stands.

Mic Stands: Six Simple Boom Stands ($22 x6)

Simple adjustable stands for the caller and musicians.

Mic Cables: Six 25-foot Colored Cables ($11 x6)

Colored cables are great for instruments: they make it much faster to diagnose problems. If you have a smaller stage you could get 12-foot ($9 x6) cables instead and have a cleaner stage and less time coiling.

Speaker Cables: Five 25-foot Black Cables ($11 x6)

Because we're using speakers that do their own amplification ("powered speakers") we actually want the same kind of cable for speakers as for mics. It's easier to think about these as being a separate type of cable, though. We want five of these: two for the mains and one for each monitor.

Misc

You should also get some power strips, 3 xlr-trs adapters for the monitors ($8 x3), and a TS cable or two in case a keyboard player forgets theirs ($9).

In all this costs about $3,700, which is quite a bit of money. Use floor monitors instead of hotspots and we're talking about $4,500. Does this much money make sense? If your dance meets once a week, though, this is about $20/dance over four years. And the system should last much longer than that [1], with occasional repairs and replacing cheaper components (cables, mic stands) as they break.

[1] The big question with longevity is the speakers. These are new designs, and none of them have been around for decades yet. I think they'll still be working well and sounding good in fifteen years, but it's hard to say.