Mike,
At that price level, you could buy a Aksa Soraya which IMO is the best ss amp I've heard. (though I would like the opportunity to compare it to a pair of monoblocked Bel 1001s).
But prior to that, I'd suggest improving your existing NuForces. Build a pair of Felixs, <$100, and bring the mids and hf, quality wise, in line with your bass.
FWIW,
Paul