the H &K edition tube (think that's the one) is meant to be nice, but I haven't tried it- i've only tried the duotone (£1500)- great cleans, unique overdrive tone. You'd need to try one, basically.
I'd say screamer or laney tt is the best bet, if you can stretch to it...
the ashdown and marshall are decent tube amps, but not much better... whereas the screamer is a very good little tube amp. Maybe not amazing compared to some of the super-amps, but still really very good (assuming you like the engl tone).
:drink:
EDIT: i haven't tried the nomads, but engls are kind of bright, while the mesa's i've tried are kind of dark sounding. They just sound different- think killswitch engage's tone (somewhat like engl) compared to petrucci's tone (mesa).
haha, koch are nice, but dear. the multitone is £1300, i think. Great, though, IMO.