Well, believe it or not, my Behringer (!) Tube ultragain MIC200 is a vast improvement for my friend's Crafter guitar with pickup (don't know the brand of the pickup). For strumming chords, it just sounds so much more powerful and less dull, it's really cool for our band when playing live. That's about the only use it gets, but it does it very very well. It's only 50 euros or so, so you could give it a try.
I'm sure there are better ones out there, and more sophisticated units, but I just thought I'd share this with you. It's an active box by the way.
