I gotta agree with Adam here: if you go wit that configuration - you definitely should shop at newegg.com With that said, if you do go 70's for the front, you'll also want to get a sub that can handle the LFE and lows, becuz the 70's are a full-range and you don't want a less-competent sub competing with the 70's.
With that said, I'm a big advocate of Polks - excellent Bang for the Buck!