I own a Trace Elliot head (AH-350SMX) with the same GP12 preamp/eq stage in it.
First off, you will find what the guy says about the wattage to be true. The rating on Trace amps is very conservative. Mine is supposed to be 350 watts, but feels and sounds like about twice that much.
Secondly, the build quality of the head I own feels like you could hang it from a crane and use it to demolish a building, then go play a gig with it.
If you like the sound, I'd say go for it, but I'd like to see you get it for somewhat less, like an offer of $450, as there is a bit of age on that piece.
BTW, there is a Trace Elliot club on TB - you might be able to find some info there.