You didn't mention it, but I was recently blown away by the Mesa Quad Preamp. They made them in the late '80's and its basically a MKII and a MKIII preamp in one box, completely isolated for 4 distinct channels. I just started looking into them after my friend got one for somewhere in the $400's, and they seem to be going used for between $400-$600US.
If they don't have the footswitch you need some kind of midi function switcher. If you will use midi, find one without the footswitch for big savings, since it needs some kind of switching to operate. You can't just push buttons to change channels. With no switch at all, you can't even get sound out because none of the channels are on! It's a pre-recto sound, but everything else matches exactly to what you're asking for. I think the V-twin and Recto pre's are lacking that classic, flexible, and versatile Mesa MK overdrive. So I'd rather have all the capabilities of the Quad.