i Have owed Krell FPB600 for about 7 years est.

I would guess there won't be the slightest bit of difference. The FPB600 is as good as it gets.

Same opinion as Irvrobinson - FPB600 is really as good as it gets!!! I used to have a FPB600, and because of my relocation to another country where voltage is 220v, instead of 120v, I had to reluctantly sell it. In my new location now, I purchased 2 years ago a new pair of Evolution 400 monoblocks, and honestly, I haven't noticed much difference, except I still miss how the FPB600 used to make the lights in the room flicker when it powered on, due to the enormous amount of current it drew, which was kind of cool!!!

I had the FPB600 and the 650monoblocks are a large jump in what the stereo amps do. That is what I have now.I match them with the BAT VK51SE preamp. I did this because I have Sound Lab electrostat speakers. The large varying impedances of the Labs give a lot of amps a fit. The monos have DOUBLE the power supplies of the FPB600.The effertless sound is hard to describe. All I can say is that there is a large improvement using the monos. I had both, this is no joke.As always the front ends are getting better.Spend your efforts there.

I am looking for a stereo FPB 600(due to space) or I would look at monos.I have talked to several people who had/has both side by side and the monos definately have better control of course,better bass and imagining,which is exactly what we strive for in upgrades.

I used to have a FPB600, and because of my relocation to another country where voltage is 220v, instead of 120v, I had to reluctantly sell it.

You should have contacted Krell. There is a 100/120/220/240V AC voltage switch inside the amp.

Well I had the FPB600 for a long time before I upgraded to the FPB650M. Although technically it are the same power amps the difference was unbeleivable. The 600 sounded broken next to the FPB600. But you should better buy an FPB700CX which plays better again than the monos.

The new generation Krell amps has better resolution and better mids.

Peter

thanks everyone
Best Regards
Chris