The Polk LSi's have a reputation for being power hogs and a significant challenge for many amps to drive - if you had the LSi15, I'd say it's a no-brainer to go with the 7500. The RTi's are not so bad in this regard, being 2dB more efficient and a less challenging 8 ohm load. You might check out the Your System Saloon forum and the "what amps and speakers" thread for some examples of what RTi owners have ended up using. As wolverine points out, the 7125 might be a good fit. I wouldn't feel bad about putting a 7500 in the system, of course (said with a 7500 sitting in the entertainment center at home...), but it's worth kicking the idea of a 7125 around a bit...