If you are primarily doing death metal, metalcore, etc. why do you need another amp? Even dudes with pretty elaborate amp collections will probably reach for the 5150/6505 with a boost 90% of the time I bet for that style.
Get good, and I mean really good at that one amp. Most bands you record that are pickier will bring their own anyway.
To round out a studio, I would get a Kemper or AxeFX. With Djent taking off and a lot of modern metal going that route, I would seriously consider one of those as your next "amp." Not to mention the workflow is stellar, no mic stands to droop or kick over, happy neighbors, etc. And you can work with multiple bands at a time on different days with a push of a button.
Now to round out a Reamping business, well then you better do your market research and the sky is the limit.
If you go ENGL, go with a Savage, Blackmore, or SE. They mic better and easier than the 'ball's. I would avoid Peavey till later. Mesa Dual Rec, Mark III, Mark V perhaps. Marshall, JVM or 800. Roland JC-120 (for cleans). Bogner Uberschall. Fryette Pitbull. EVH 5150III. At some point though honestly, things even out pretty quick.
It is like the stink on the cheese. Yeah there are differences that depending on the person ranges from subtle to drastic. But the fact is, it is still stinky ass cheese!
