6505. 100% Brutal amp.
However, if you can find a Marshall 8100 Valvestate head, that's well worth it. Fairly budget too.
HM-2 into Marshall is pretty much old school death metal. Marshall valve heads turned all the way up is Motorhead.
At one point I used a Marshall Shredmaster into JCM900 which was kind of silly. Pity that Shredmasters are going for stupid money now, they're great dirty/thrash pedals. £150 on ebay?? HAHAHAHAHAHAHA. :?