Help with Pre-Amp

I am looking for suggestions what to use as Pre/Pro for my system. I currently am running a pair of Revel F52s----C52 Center with an Emotiva xpa-5. My Onkyo TX-NR801 is serving as my Pre/Pro and am thinking this along with some surround speakers will be my next upgrade. Anyone familiar with these speakers your opinions would be greatly appreciated. Sound improvement is # 1 priority.. Thanks everyone!!!