In 2008, I bought the Klipsch Quintet SL set, and have enjoyed them (with the exception of low vocals from the center channel). Newegg is having a deal on the Polk Monitor Series II M60 ($100 each).
What I'm trying to figure out is if an upgrade from the Quintet SL to the Polk Monitor Series M6 would be a true upgrade in performance, or just a matter of personal preference (Klispch vs Polk).
Some additional info: I'll be running the speaker setup in a 16x13 living room in an apartment. Receiver is a Yamaha RX-V667, and my subwoofer is a very old and discontinued Yamaha YST-SW320.