Exchange Krell KAV-250a for a Pass Labs X-350?

I agree with Gregm: the Pass is probably the better sounding amp, and IMO, if its available to you for the ease of a swap, I'd do it. However, I'd guess you'll notice a bigger difference by upgrading your preamp. NAD is ok but not in the same league with Pass/Krell and Dynaudio.

Yes, that is the pendulum Gregm. I do not know yet. But the general consensus is that the Krell may be a bit sterile or have a sound. I am just looking for my next upgrade path if I need one. I have tried a number of preamps, tubes and SS, and I have landed with the NAD Silverline but I also restrict my self to a budget. So I am looking for people who might say, Yea, I know quite a few people who have had that problem or this with that and they changed to ?
My sources are the Silverline S-500 CD and a Project Perspective with a Blue Point Special. Dale

Mg123, I do not think that your statement about the NAD Silverline preamp not being in the same level as the Krell, Pass, or Dynaudio is in fact. The S-500 is a different animal than the regular NAD equipment. The Silverline is NAD's bid at the highend. I chose it over the Krell KAV-250p and others. It had a much more balanced sound and it's build qulaity was a notch better. It's Danish heritage was very evident. I don't know why the Silverline suffers from PR problems but it could have something to do with NAD not giving free samples to the American audio media. They make them buy the samples. Go figure. But after going through a few preamps to buy the NAD was the winner in overall sound quality so I was not focusing on it. Dale

Would you borrow the Pass amp from a local dealer? Try a Pass X series pre-amp first. They are truly balanced - like the X 350. I think the KAV-250a is truly balanced?! You might want to try an Adcom GFP750 pre-amp also. It has single ended & truly balanced inputs & outputs, & was designed by Nelson Pass, who founded Pass Labs. I use the GFP750 with my Rowland Model 2 in balanced mode & it works quite well.
I've seen the NAD pre amp at a local dealer, I believe it is "psuedo balanced" which means although it may have "balanced" inputs or outputs, they are coverted inside the pre-amp to single ended anyway. Check the input & output impedance numbers. The Adcom input impedance measures 94k ohms balanced, 47k ohms unbalanced. Output impedance 1200 ohms balanced, 600 ohms unbalanced. When the balanced value is double the unbalanced value, the component is "fully balanced" or "truly balanced".
I also own a Pass Aleph 3 amp, it is single ended only, when I use it I run the variable out from my SONY XA7ES directly into it.
If I were you I'd give the Krell another chance with a better pre-amp.

Dale, you mention "sterile": to me this sounds like you're questioning the KAVs tonal balance & musicality in yr system. IMO, try the X-350 on this system; listen to light jazz & classical, and check out the X's tonal balance vs. the KAV. You want to be drawn into the music -- i.e. does the Pass render subtle musical details more realistically to your ears? Do the little sounds "make sense", are they indispensable to the musical piece -- or could you have dispensed with them? If they do and are, and didn't and were'nt before, keep the Pass!

Three people I know (who found the KAVs a tad "dry" to their taste) ultimately chose Pass, YBA, Atma-sphere. Pls note, however: COMPLETELY different systems!

Cheers!