I'd recommend Stan Warren of Supermods. He is prompt, knows his stuff, he is the S in PS Audio, not sure why he left, I think it may have been family related. Then he started Superphon, grew tired of manufacturing, sold to Audio Advisor, who did not know how to run the company apparently. Then he started Supermods.
2375 W. 21ST Ave.
Eugene, OR 97405
Tell him you want a Hexfred bridge, all 1N400(1,2,4,etc.) diodes replaced with UF1N4007's available from Mouser, made by Fairchild. If he has problems getting them I'll be happy to give him some. Then the poly caps should be replaced with AudioCap Theta's or MultiCap RTX's, the RTX's are a little better perhaps, but a lot more money. More can be done for sure, replacing the RCA jacks and mounting them on a plate would be a really good idea, but I do not know if he would do that or not, you would have to ask.
Then you need to buy Bugle Boy tubes for a MAJOR audio thrill! This presupposes that the rest of your system has the resolution to hear all the improvements. I have NO doubt that you will hear improvements, but how much will vary with your other associated gear.