Tube Amps who does mods and upgrades?

looking for a competent center or individual who could peform sonic upgrades for tube amps.PREFER name AND PHONE #.thank you.
The Great Northern Sound Company in MN does great work. Steve Huntley was with Audio Research & Wadia and has vast knowledge on the topic. 651-578-0657 Tell him Tim Fox in Des Moines gave you the tip. Good Luck
Tim Fox,thank you very much for the info,It's just what i needed .
Your man is Bruce Wenger at BWS Consulting. Call him at 703-536-3910
THANK YOU Priority for the info.
I second the recommendation of Steve Huntley/ Great Northen Sound. He is The Man. Lots of integrity.
Would like to add my name to the list of Steve Huntley supporters. Integrity is the word. He is also a nice guy who knows a lot but doesn't think he knows everything. We need more like him.