Audio Research LS-16 unpgrade

I currently use the LS 16 as the front end of my 2 channel system consisting of VTL 150 amp, Silverline Sonata speakers and Audioquest volcano speaker cables. It is the mk.1 version (6922 tubes) and I would like to know if it is worth spending the extra 1K on the MK.11 version (super tube). Does anyone have experience with this upgrade and what are the sonic improvements? I have already switched to NOS tubes from Upscale Audio and the improvement was well worth the money.

I run an LS16 MK-II in my bedroom system. It's nice but I don't think I'd spend a grand for the upgrade. I don't think you'll get the re-sale value out of the piece later. I have a real hard time paying for factory upgrades because it means paying full retail. You could probably find a MK-II for under $2000.00 in the used market.
I have asked the same question before(I have LS-16 as well.) Nobody has ever posted any experience with the upgrade to MK-II.

I am due for replacing the orig tubes. Cavy, Which NOS did you get from Upscale and what improvements did you notice?