Dagger's bringing out a new Mamba soon, so all the older models are going cheap. I have a friend who just got one for £650 brand new. A very good boat.
There's Pyranha Burn, which is expensive, being a relatively new model, but it has a large following and is a great boat, slightly catchier than the mamba.
I have to admit, the Karnali just seemed too big, slow and HEAVY for me, but try it anyway.
Dagger also have the Nomad, which just about trumped the others in a recent competition, but more expensive again. Personally I preferred the other two, anyway.
Another one to look at is the WaveSport Diesel. Its a bit more, shall we say 'Industrial' looking, more angles than curves, and it seemed a little wallowy to me, but maybe thats just me! I've heard great things about it.
My local shop doesn't stock the Jefe, or any other brands except Jackson, so I can't speak from experience about any of thier boats. If you're down anywhere near Hampshire, go down to Woodmill Canoe shop to try these out.
One more point though - don't forget to test what the boat's like OUT of the water, i.e. carrying it and transporting it. I've seen too many people buy a boat then complain it hurts their shoulder or won't fit on the car...
Happy hunting!