Does anybody have experience or knowledge of the best available modifications for the Quad 405-2 amplifier?

There are several companies offering mods, such as replacing the power caps, op amps and generally bringing the design up to date.

I like the Quad very much and it drives my Audio Vector M2's well, but in the never ending quest to make improvements (the budget does not extend to a new power amp), are the mods going to make a significant difference?

Also, does anyone recommend a particular company or service to carry them out?

Thank you in advance for any help in this matter, or any other suggestions as to how my system may be improved on a fairly tight budget!