Alright, so here's my sob story: kid without a job, bought a tiny used Fender combo amp--probably 10-25 watts--that I knew nothing about when I still couldn't remember standard tuning off the top of my head. I've pretty much grown out of it, I'd venture to say. Now I've got myself a rock band, and I can't even hear myself at practice. At ALL. At gigs, I always feel weird, because I'll usually borrow someone else's amp, and I'll hear this strange sound in our songs and realize, Hey, that's ME! Thus, I'm looking to buy a stack that I won't need to upgrade for a while, on a budget that has yet to exist. (I only have a $1.50 to my name as of now, looking to get some employment soon-ish.) I'm thinking a Yorkie XS400H'll do quite nicely--I hardly play larger venues, but I do have outdoor shows a bit regularly--and from what I've read around here, Avatar cabs are the bomb for their price, but what I can't figure out is this: Which types of speaker arrangements are for what kind of sound? What advantages and disadvantages do 4x10's, 2x10's, 1x15 or 18's, and 1 or 2x12's have over each other?