Although it's only part of it, theKorn has a great guide that got me started on speaker selection and backbox speakers...

http://www.thekorn.net/speakers/

After that and a little more research, I was able to start doing upgrades myself. For my upgrade, which was only the sub, I think I paid about $90... but it was enough for two and a half machines. I've only done one so far, but if I ever stop being lazy I'll probably swap out my Iron Man kit that came installed with it with mine instead.

You do have to figure out some stuff for sure, so the FF kits are nice if you don't want to do that.