Tha RCA inputs on the amp are for inter-connecting with the preamp/receiver pre-out channels. You then power your speakers with the appropriate amp speaker connections instead of the receiver's. RCA connections are unbalanced and may but not necessarily induce some hum in your system depending on other equipment. Xlr connections are balanced (no hum) but require the same connection types on both source and amp.
Sounds like you are considering powering a 3.1 system or planning on sharing amping duties with your receiver for some channels. Either way you go, try to get something which gives around 200W/channel. You can go with less but my experience has taught me otherwise.
Sounds like you are considering powering a 3.1 system or planning on sharing amping duties with your receiver for some channels. Either way you go, try to get something which gives around 200W/channel. You can go with less but my experience has taught me otherwise.