Best amp for B&W Nautilus 804? Looking for advice.

Howdy,

I own a pair of B&W Nautilus 804's and I'm looking for a new (used) amp/preamp to drive them. I'm currently using a Classe CAP-151 which is adequate but I'm looking for more. Looking for a broader, deeper soundstage and a live, real sound (at least as much as my budget will allow).

Right now I'm looking on the used market for one of these three set-ups: 1)Classe 47.5 Pre / CA-301 Power; 2)Krell KRC3 Pre / FPB200 Power; 3) Krell KAV 500i. Any other options in this price range?

Don't have a krell dealer in the area so I can't audition. Hoping anyone familiar with that equipment will offer their opinion.

Thanks all, John