Well hell, thanks for all the replies guys, that's a lot to think about!
I don't have anything horribly ultra-special, my prize piece would be either my SLO-100 or my Granger GNR-10036 (It's a hand built reproduction of the Super Trem with the Caswell mod used on the AFD album, along with a slew of others back then). Cabs are nothing special, couple of Orange 2x12's, a 4x12 and an Avatar cab with Alnico Blues in it. The rest are basically standard stuff, a 100w Silver Jubilee, DSL, AC30, that sort of thing.
I'd lean towards keeping the Granger really. Curt's a personal friend and it's not only the prototype for that series of amps he sells, but he tweaked it a bit specifically for me, so it's more an heirloom than 'I can't live without it' (heirloom might be too strong a word, but it's definitely got sentimental value to me).
As far as amps being invaluable in the studio, generally I agree with that, BUT (and I'm in no way denigrating myself here, just being realistic), nothing that _I_ do, or ever WILL do in the studio is going to be to that N'th degree that a tube amp might provide. Not that I can imagine anyway.
Definitely something to ponder, but I have a feeling I already know what I'm going to do.