HT Options
It is not necessary to match up the power rating of the receiver to the speakers. In your room, anything over 100 Watts / channel should be adequate to drive the Polks or any other moderately efficient speaker. Also keep in mind that doubling the power (100 Watts to 200 Watts) will only cause a 3 dB increase in volume making it "slightly louder".
For mid-fi receivers, you should check out the Yamaha RX-V2600 and Denon 3806. Both of these manufacturers have better reputations then the Sony receivers. If you really want 200 Watts / channel, then you sould consider an outboard amplifier with a receiver or pre-pro.
The LSI's are one of the better polk lines. In your budget, you should also consider auditioning Paradigm, Axiom Audio, PSB, Klipsch Reference, and other manufacturers.