Krell Trio 300 vs. Krell Trio 300 XD

The XD upgrade is easily worth it. There is a lot more information,"detail" being reproduced. You will certainly notice it. 

I"m not sure. I don't know what amp solid state amp would be considered less bright than the new Krell amps XD or non-XD. I'm a long time Mcintosh amplifier owner. I'd say the Duo 300 XD is not any brighter than the new Mcintosh MC611. Never thought I'd be saying that in a comparison of Krell and Mcintosh. If I had to pick, I'd say the Duo 300 is less bright then the MC611. The "house sound" of both companies seems to have moved in opposite directions from their old sound.

I was able to compare both XD and non-XD in same system. The tonal  characteristics don't change. A lot more information passes through the XD than the non-XD. Imaging is a lot more 3D in XD and that's where the greatest improvement is for me.  I missed my Mcintosh monoblock's imaging before hearing the XD model. Now I have what I always wanted my Mcintosh to be,  extremely dynamic, tube-amp like imaging , and non-fatiguing. 

I have Mcintosh XR200 speakers and while I love the speakers, I always felt I would like a more dynamic speaker. I've tried a few brands but none were able to change the fundamental dynamics of the speakers until Krell both XD and non-XD. The Krell amps were already dynamic and I don't hear much difference there between XD and non XD.

The only set-ups that match the Krell XD stuff is bi-amping with a tube amp on the mids and highs and a dynamic solid state amp on the bottom end. The Krell XD stuff can just do it all in one box.

nd_72, I concur with your assessment of how the amps come back. My 300Duo XD certainly came back looking brand new as well .Krell really did a fine job.