[jackfish]

For that price the Polk LSi15 is definitely worth it. However, make sure you can get a matched set of right and left towers. Unfortunately, the Polk CSi3 is a big step down from the LSi15 which has the LSiC as a companion. I'm not thrilled by the CSi3 or the RTi4s. I like the Infinity Primus PC350 and P152s better. But if you listened to the Polks together and liked it, then that's all that matters. The price on the pair of RTi4s is also a good one, but you should be able to find that center for $150.

The real problem with the Polk LSi15 as you mentioned is power. They operate at 4 Ohms and have an 88dB sensitivity both of which suggests to me at least 100 watts RMS @ 8 Ohms of clean power per channel. What receiver do you have?