gfp-750 ? any comments? good or bad

I think the 750 would be a great choice for your given system. I believe it deserves it's class A rating. It is very very quiet, even in active mode. I agree that the pass labs preamp is better, but it's not a world of difference. If you can live without a remote, the pass labs aleph L and the mccormack passives are very good as well. Nice thing about the 750 is that it is easy to buy a nice one used, and equally easy to resell. It will also be newer.

I agree with the more positive posts. Owned one for a couple of years. Very quiet, not additive, very flexible. I took a big step up and, yes, there is a difference, if you want to spend a lot more money. Class A? Well, maybe not, but damned good none-the-less.

If your choice is a new one, I think you'd be better off getting the real thing: a used Aleph P with remote, for not much more $$.
OTOH I was SO disappointed with the N804 (specifically produced for the American market to meet a price-point as an afterthought by B&W!), that I have to suggest you try what I think are better speakers around the same price, like Revel F30, Aeriel 7b, Thiel 2.3, or any of the others Audiogoners would suggest. Sorry...just one guy's opinion, but I believe your weak link is with your loudspeakers incoherence and weird spectral response, and not with subtleties in similar preamp designs....