Audio research LS25 any opinions

I have been thinking of buying an LS25 and than eventually upgrading it to the mkII version. Can anyone give me some feedback on newew AR pre amps.
I own a Ref 2. I'm not sure I want to upgrade and have SS components added as well as different tubes. ARC has been having problems with Sovtek 6992 so they are dumping 6992. I use NOS Mullards and they work great. The LS25 is an excellent preamp, I'm not sure the MkII is really better.
I use the LS25 mkI with a VT100 mkII. The como makes great music. Some people have been critical of the MKI. However, I have been very happy with its performance: Transparent, neutral, open, dynamic, smooth, musical, great soundstage. How does the LS25 MKI compare with the LS25 MKII?
I've got one too. Think it's great, but realized significant improvement by using different nos tubes
I too, am very happy with my VT-100 mk2 and LS-25 combo driving Watt/Puppies. Can anyone recommend best NOS tubes to try with LS-25? I am unable to afford the mk2 upgrade at the present time and would like to experiment with NOS. And also best place to purchase NOS tubes? I am running the supplied 6922's now. I Can also Highly recommend Marigo dot treatment and the Top Gun power cord for LS-25. Any suggestions on NOS tubes is much appreciated!