Who does best SS preamp modifications?

Better to sell what you have and buy what you want. At $2400, the Rowland Capri is very hard to beat.
State a price and ask for recommendations. There are a lot of great used products for sale on here every day.
Two names I would look at, depending on budget are Klyne and Marsh.
You never get your money back when you sell modded stuff.

No need to sell if it sounds the way you like it Angela.

One thing that I would strongly suggest, is to match your preamp to your speakers/amp of choice as well as your personal taste and preferances. It would make perfect sense to call the moder of your choice and ask him for suggestions that best fit your needs. What you get for your money is not only the upgrade but his knowlodge. There is a lot of guys that do mods for living, however not all know what they are doing. Those that do,can be found here and you can read about their work based on those that had some work done on their unites.
Check out Bob Backert thread. Highly recommended.

If it sounded the way she likes, would she be looking to modify it? Maybe, I don't know her, but I suspect the reason behind the question has "dissatisfaction" in it somewhere.

Mod is short for modify. Modify means change. Change means make different. It does not necessarily mean make better.

Often when one looks into this course of action it is in the hope of finding a miracle or a bargain. Generally speaking, you will do far better by applying the "mod" funds to a real upgrade. Unless you have a quantifiable and well-known mod done, you will never retrieve the investment upon resale.
Sad fact.

If, on the other hand, you make a smart purchase on Audiogon, you're chances of reselling the next preamp at no loss are very good indeed.

Pick your poison. You weren't asking for this kind of advice but I hope you think about it anyway.

Macrojack in all due respect.......It wasn't exactly what Angela was asking.....was it.

You don't see me pushing anyone straight to the most recent adds on AgoN unless someone ask me privately.....do you???

Another thing. Modifications goal is not to overhaul , dramatically change or alter the piece of gear in question in the matter that would change its character or signature qualities and sound. Every idiot can do that. The art of moding is to improve on already good design and squeez the last bit of performance and/or lightly season to taste. IMHO

If Angela is interested in older or vintage designs she must have a good reason to do so.
If someone is interested in SS preamp, amp or whatever....I don't try to force on her/him my own preferances - which are tubes but away. Since Angela is not as seasoned as some here on this forum ( including myself ) it would make sense to give her the freedom to learn, ask questions and let her decide what is best for her.

Angela, if you are tring to put together nice rig without breaking the bank there are few excellent choices out there which can be had or be build to your specification and taste for well under 1K. Shot me an email - I will be more then happy to talk to you about those option.

Best regards
Mariusz