Tweaker's Asylum

I brought home a few weeks ago a Yamaha RX-v793 receiver (80 watts per channel) with Paradigm Studio 20s and the matching CC-450. I have a low pass connection (via a single RCA Monster cable) to a Velodyne 1015.

The Paradigms sounded so sharp, crisp, clear, and dynamic in the store. They have phenomenal imaging but the almost never sound very sharp and crystal at home. The room in which they are is 10' wide by 11' long with only three walls---it is an open room.

I understand that audio shops have ideally designed acoustically optimal rooms and I don't.

Is this Yamaha properly matched for my speakers ?

Do I have enough power ?

I bought the Yamaha as a floor model. It seems ok, but could this be my problem ?

What can I do to significantly improve the sound ?

Please help.

Thanks.