IMHO, I think you would be better served upgrading your preamp. There are many preamps that will leave your Sony preamp in the dust.
HOWEVER, if you are set on a new amp... I have had the Plinius SA-100 mk3, the Sim Audio W-5, GamuT D-200mk1 and mk2, I have heard the Pass X-250, and I OWN an Ayre V-5x. I think the V-5x in many ways is one of the best solid state amps under $6k retail. The V-5x may only be rated 150wpc, but it SEEMS more powerful than the W-5 or the Gamut amps I have had. At $6k retail there is some serious competition in the 200wpc+ amp category: Parasound JC-1 Halo amps, Rogue Zeus monster tube amp, and the McCormick DNA-500.
KF
HOWEVER, if you are set on a new amp... I have had the Plinius SA-100 mk3, the Sim Audio W-5, GamuT D-200mk1 and mk2, I have heard the Pass X-250, and I OWN an Ayre V-5x. I think the V-5x in many ways is one of the best solid state amps under $6k retail. The V-5x may only be rated 150wpc, but it SEEMS more powerful than the W-5 or the Gamut amps I have had. At $6k retail there is some serious competition in the 200wpc+ amp category: Parasound JC-1 Halo amps, Rogue Zeus monster tube amp, and the McCormick DNA-500.
KF