There are three modelling amps that I'd use as a practice amp. One is the Peavey Vypyr 30w, next is the Vox VT30 and finally, the Roland Cube 30X. The Vypyr just isn't cheap enough yet and between the Vox and the Roland, I'd rather have the Cube. £80-100 on Ebay seems to get you a good one, though you may get one for less.
