Manley Jumbo Shrimp upgrade

Why don't you start by replacing the fuses with SR Black fuses and see if it makes a big improvement before you invest bigger dollars?

Unless someone knows a tech who has a tried-and-true proven mod for that particular piece, I would stay away from it.  Replacing parts with more expensive parts may not yield the results you're looking for.  You have a tube preamp, how about rolling the tubes for starters? I'm sure you could get some good recommendations here or from Andy at Vintage Tube Services.  

I would save up for the U/12, or better yet the U/10 mod/upgrade.

DeKay

I agree with lak and chauro. Manley makes great equipment. Just letting someone upgrade your already well thought out and built piece of equipment is risky! Try a fuse and tube rolling First! Save your $ for the "Real Deal" I have a Steelhead and am just finding out how good it is after nine (9) yrs. Take your time. Enjoy what you have. It's part of our Journey. Best Wishes.