I'm not a 6505 owner, but I've played a handful of them and they were all pretty noisy at higher gain levels. Putting a noise gate before and/or in the loop of the amp is a great fix for this. The Mesa Triaxis is a similarly noisy preamp, and I had to have a solid noise gate between it and my power amp when I played live with it, and I don't even really use a lot of gain. My Triple Rec needs a noise gate in the loop as well and it's whisper quiet in between palm mutes as a result.
Noise gates = good
Chances are if you bought it new, the tubes are fine. I always am a fan of a Tung Sol in V1 because I think it really helps the sound in any amp, but other than that if you bought it new, it's what Peavey wants the amp to sound like, and that's generally pretty great.