I'll second the recommendation for HK Audio Lucas systems - I recently bought a Lucas 1000 which I use with my ceilidh band and I'm really pleased with it, it gives a very clear sound and fills a lot larger space than you'd imagine for something so compact. I've used it with vocals too, the first time was with an unaccompanied singing trio and from the back of the room it was totally audible but quality-wise sounded as if they weren't even going through a PA. The 1000 has the same size top speakers as the 600 (150W each) but a larger bass speaker (600W and capable of making a lot of noise).

Charley