of course, for metal.
I am a little biased considering I own one, but I would go with the 6505. You might want to get a retube though. It still sounds great with the stock tubes, but it will make a world of difference to pay an extra $150 or so for JJs or something.
Powerball seems like the better option here. Apparently, it has ridiculous rhythm/lead channels and also has a very nice clean channel. It's also $2000 for the head - more than a 6505 half-stack. So you'll definitely be getting what you pay for, but if crystal-clear cleans aren't of importance and you just want a high-gain amp, the 6505 will do the trick.
Powerball if you want to use something aside from brutal metal distortion ie cleans, varying forms of crunch, etc. Plus, i believe it has a built in noise gate, along with some footswitchable modes (?), so that would make it a shatload more versatile.