Not so sure about the AVT - Low end Marshalls don't cut it for me at the moment.
Haven't heard much or anything on the Randall :S
H&K make a tube amp for about £400, 20w, 1x12 combo.
I think you can get the 5w Peavey that Satch endorses for about that aswell, which is meant to be ace.
Laney LC30 combo is about £400 I think - Never played one but Laney's tend to play nicely.
Best thing you could do is get a 2nd hand high end amp though. Look around on places like Ebay or if you have contacts in the US, (Which I've heard you saying before) then you could get a great deal.
Edit: I have the VOX AD30VT - Don't get it. Sooo much better out there, and the stupid amount of amps makes it impossible to use with pedals.