Preamp modifications - who would you use?


I am looking for a company or individual who performs equipment modifications to take a look at a preamp I own and recommend (and implement) parts improvements and or modifications to squeeze out the last bit of sonic performance. I would like to talk with someone who is well regarded not only for the quality of their work but also for their customer service, and who has enough experience and expertise to assess each piece on an individual basis, and not simply apply the same bag of tricks to everything they touch. Based on things I have read, folks that come to mind are Kyle Takenaga at RAM, Bill Thalman at Music Technology, and Chris Johnson at Partsconnexion. I would be interested in other recommendations. Thanks.
mitch2
Phaelon is right on. I can't imagine better results than can be obtained by Bob Backert of RHB Dezigns. Bob will analyze the circuit design and implementation and recommend what he can do and how each improvement will effect the sound of the gear. Bob tests with equipment and ears all along the way.

Bob is professional and the consummate gentleman. He and his son do great work! You will not be disappointed.

If you check around on the net I am confident you will find nothing but rave reviews of RHB.
Check with Joseph Chow at Audio Horizons. He designed and developed one of the most highly regarded preamps around. He has a separate upgrade (mod) business unit, and will make a recommendation once he's assessed your gear. I have been very happy with his work ... great customer service and he'll give you very reasonable rates.
Thanks everyone, you have come up with some names that I didn't know about. Any more I should consider?