Audio Research SP9 MKII to MKIII Upgrade

Has anyone done the above upgrade to their Audio Research SP9 MKII preamp?

Were you happy with the results?

Were the improvements significant enough to justify the cost?
The jump in quality from MKII to MK III is substantial, and well worth the cost. However, it's cheaper to do what I did-- sell my Mk II on Audiogon and buy a used Mk III. I probably paid $150 for a mod that would have cost $800 if I'd sent my unit back to the factory.

If you're seriously considering moding your SP9, you might want to chat with Steve Huntley at Great Northern Sound about it. I had him mod my SP9 MKII to their Reference level which I have been extremely happy with. While not cheap, there are a number of things Steve can do that I suspect would easily beat out the MkII to III upgrade. Contact info can be found at Definitely worth an email or phone call!
There is a Mark3 for sale here at $900. there are two Mark2's for sale at $635, so it seems that you may want to consider Swklein's advice.
Apparently ARC can also add a remote to the SP9 for about $700. Ouch!!!
More curiously though is how well the SP9 mkIII or modded version would compare to say a newer sp16 or the like. It seems as though modding or upgrading is really pricey and there are quite a few newer models available on Audiogon for less than the cost of the mods.
I'm asking because I am considering an SP9 myself.
Try listening to the amp with 7308 tubes instead of the stock 6DJ8. I'm using Gold Aero Platinum Grade Gold Pin on my Mk II.

One cheap mod that makes a big difference is using fast recovery diodes in the power supply.
I had the MKIII upgrade done a year ago. There is a noticable improvement in sound quality, that I believe was worth the $800 cost. While the advice to sell your MKII and buy a MKIII on Audiogon is economically sound, I should mention that ARC included a really nice screwdriver when they returned my upgraded SP-9!!!
There is an audio research sp-9 MKI for sale and would like an mkII or an MKIII , however is starting out with

a sp-9 mk 1 to a mkII worth it or go out and buy a mkII directly or sn MKIII?

First time here so Hello to everyone.