What's it being used for? Home practice? Recording? Gigging? Venue size? All genres, Rock/Metal?
The only amps I've found to cover lot's of tonal bases on a footswtich...
Rackmounts JMP1/EL34 50:50 Marshall, ADA MP1/EL34 50:50. Both Rackmount systems. Okay clean/crunch, okay overdriven, nice distortion.
Mesa Mark Series (IV/V). Nice clean/crunch, nice overdrive, okay distortion.
Rivera Fandango - Nice clean, Nice od, okay distortion.
Some of the hugehes and Kettner big ones ar supposed to be nice too...
For me, if possible I tend to prefer single channel amps (Vox AC, Fender DR, marshall Plexi).
But in a covers project thats not always viable so when I need a selection of sounds I use a Mesa Mark IV (at the Moment

) . (Although I'm looking at a JMP1 into PA (i.e. without the bloody heavy power amp!! Man, they are so heavy! Not again!) for times when I need to travel even lighter/smaller!

)