If I played thrash and did not care about a clean channel, I would go for a 800 2205/10. If I wanted a better clean, I'd get a DSL.
This.
I know a couple west coast guys, that told me the 2205/10s were the amp of choice for many early thrash scene bands at clubs. The post 1985 versions have a shit ton of gain; as long as you run them with the gain maxed and chan vol maxed..ch vol acts like a gain 2. Then, there are 3 small easy mods you can do (if the amp isn't perfect as is).
1. Clip the treble bleed cap (C20 on my 86 2210)-less tubby sounding.
2. Move the purple NFB wire to the 16 ohm tap(yellow in mine)-tighter response
3. Re heat ALL the solder points on the pots. You'll have to remove the knobs, washers and gently push the board back to get to the points but the amp utterly wakes up after. The board is literally held in place by the pots...no bolts/nuts like the 70s versions. Over time those solder points just don't work well like when new.
The clean channel is more like the regular 2203/4 channel in that it will be dirty....maybe a detox pedal or just working the guitar vol. The DSL definitely wins the clean channel contest here.
The 2555x is my 1b to the 2205/10....they are really killer and DO have a great clean. I give the nod to the vintage 800s because of the iron. I'd choose the 2555x over the DSL though, since the clean is very good but the lead channel is better to me than the DSL.
But that's my preference.