Re-tubing my ARC reference 1 preamp

You will get warmth with those Mullards. Good sources for NOS in my experience have been Brent Jesse and Vintage Tube Services. Hardes part is getting closely matched and balanced pairs, but these guys seems to do a good job.

Has anyone ever dealt with "VINTAGE TUBE SERVICES" if so, what is your experience with Andy?

I bought a matched pair of Amperex White Label and they sound great in my amp. Since I don't have my own tube amp measuring equipment, I have no idea whether or not the tubes measure as he says, but he has a reputation for being fanatical about measurment and quality. You probaly need to hear from someone that has measuring equipment to know that what Andy says he is selling measures as he says. All I know is they tubes came as described and sounded very good in my amp.

There are a handful of good tube vendors but if there's anybody better than Andy, I've yet to transact with him/her.

Buy in total confidence.