I never checked it out in person, and I don't really have any advice on what to do about the hissing. But typically Peavey amps are built to last the apocalypse.
I've got the Peavey Musician 400 head, the all-purpose version of that amp and it's really starting to grow on me. It's loud as hell too. I've read that the "Bass" versions of these heads are noticeably better sounding for bass than the "Musician" heads (Go figure) and I that appeals to me since I already like the Musician series.... But I need another amp like I need my girlfriend to bitch at me more, so I'd love to see the seller take down the posting. Go buy the amp!
Don't sweat the petty things, and don't pet the sweaty things.
Acoustic Amp Club #364