Hey guy, I see that you bought on my rec, hehe.
Matrixing creates sound to the surround and/or rear speakers that would normally not have any audio sent to them. A "faking out" of sorts. So, I believe crizz is talking about, for instance, a 5.1 audio track, but not having the ability to get sound from the "rears", something it seems you don't care about anyways. Remember "surrounds" and "rears" are not the same thing, as in 5.1 vs 7.1
I thought the 605 was $145 more.... only $100, where please?
If you have the money I think 605 is a nice future proofing for the internal decoders of TrueHD, MA, etc. (Please don't ask me what they are).
I recommend you order from Monoprice -NOW-, so that everything is ready to hook up when the stuff gets in. Even Radio Shack on sale is quite a bit more expensive, in my experience.
Lastly, the one place I recommend you blow more dough (if you have it) is on the sub. No reason to skimp, at least not to me in terms of "going about this lightly". Get a better sub. How about Hsu Stf-2 for $350? Whatever, good luck.