Mod Recommendations?

I'm getting a Mark Levinson 333 amp and am considering having it modified to 336+ status. There seem to be a lot of folks who are doing mods nowadays. Many of them charge an arm and a leg just to solder in a few caps and resistors.

I'd appreciate recommendations or advice from members who have some experience in this area and can point me to modifiers offering the best bang for the buck--and who know what they're doing.

Often times you get what you pay for.
The experience needed to know what is right and better, as well as the steady hand to do it has value beyond the parts and time costs. Also, the value of the item against the value of it if in case the origional manufacturer cared enough to in some cases build it right the first time must be considered.
Unless you want someone who is unavailable, sitting in a sweat shop, most good mods are rightly valued against what you'd pay for the item new. If the $4000 d/a is made to sound like the $6000 d/a the mod persons know that you'd buy the more expensive one if their work wasn't available.
So they should rightly charge somewhere between the two depending on the parts, time and experience needed.
Great Northern Sound has been able to work with manu's to keep waranty, and allow the unit to keep authorized value for resale. In some cases, have the guy down the street do the work is like throwing it away if you ever try to sell.
Seek them out, and you'll find that GNS asks a high price. But I've heard very good things about them.
Also, Bob at World wode Stereo in Ardmore PA is a very knowledgable designer .