#1
I am considering getting an attenuator for my 6505+. However, I have read that attenuators can suck tone, and are useless for amps that rely on preamp gain for distortion. Is this true? Would I be better off without an attenuator for my 6505+?
Peavey 6505+
Marshall Jcm-900 Lead 1960 cab
Jackson USA RR1 w/SD blackouts
Jackson Dominion w/SD Distortion
Jackson SLS3 w/SD blackouts
Maxon OD808
EH Small Clone chorus
Ampeg B2R
Ampeg Cabs, 4x10, 1x15
Rickenbacker Bass Guitar
Ibanez CP-9
#2
I've heard the first part (tone-sucking) but not the second (useless for preamp distortion). I still think the attenuator will give you a much better, more usable tone than without, but only because it's virtually impossible to crank a 6505 outside of a soundproof room :-).

I've not played a 6505 much, so I can't say much about its gain sound (I'm guessing heavy and awesome). I can say that I've had 4 amps (Hot rod deluxe, Marshall 6100, epi valve junior and a Peavey JSX) and having an attenuator made every one of them but the deluxe sound much better. Bottom line: if you like the distortion of your amp, it only gets better by cranking it, and a good attenuator (Weber, ultimate, etc) will get you close to that cranked sound.
#4
Well I just remembered that my friend has a THD hotplate that will work with my amp, so I am going to test it out here in a few mins, I will let you guys know what I think.
Peavey 6505+
Marshall Jcm-900 Lead 1960 cab
Jackson USA RR1 w/SD blackouts
Jackson Dominion w/SD Distortion
Jackson SLS3 w/SD blackouts
Maxon OD808
EH Small Clone chorus
Ampeg B2R
Ampeg Cabs, 4x10, 1x15
Rickenbacker Bass Guitar
Ibanez CP-9