Musical Fidelity fine-tuning service

Own a Tri-Vista 300 integrated amp, I can see several things that can improve this great amp to world class.

Musical Fidelity offers similar service and take it to the extreme, they will install better parts, adjust and match, replace and repair, etc for £599 inc. VAT. Sounds reasonable considering the amount of work involved, but shipping is prohibitly expensive when you have to pay shipping both ways.

Has anyone explored this option or try to mod it yourself to similar effect?

http://www.musicalfidelity.com/tuning-information.asp