Just FYI in case you don't know, Best Buy now price matches.
Also, yes, a center channel does most of the voices when one is used in a surround sound setup. A center channel is a big deal, so normally you get as big of a one as you can. For example, 3 towers across the front would actually be better than 2 towers and a smaller center. Most people can't fit a tower in the center, so the chose a center designed specifically for that duty. You see some people go with bookshelfs, and a center, where the center is actually bigger than the bookshelfs.
Yeah, the center is very important. It's hard to do this all at once with your budget. I still think starting out with 2 good speakers is the best (as opposed to a cheap 5.1 setup) if you do indeed plan on having more funds to throw at it in the future.
Just remember, chances are, if you start out with just a pair of bookshelfs, you might feel the low end bass stuff is lacking. That's why myself, and others have recommended just starting out with towers, because that will give you a little more low end, generally.
Also, others could maybe comment here, but with a baby crawling around, I'm not sure but a tower might be a little safer than bookshelfs on stands...IDK.