IMHO and finite experience. First, there is no substitute for common sense...
If you want to control costs and get a guaranteed outcome, the best bet is to go with an established "name" modder and mod a unit he already has experience with or has "productized".
There are three problems this helps to overcome:
1) Since most manufacturers don't put up their circuit diagrams etc, there can be a long period of discovery with a new unit as the modder figures out what the guy ahead of him did and didn't do - and why. That can get expensive
2) In theory, modding involves a certain amount of critical listening and fine tuning. When a modder does the same mod on an ongoing basis, you gain the benefit of his experience and evolution, as well as all the other owners feedback. This gets you a better unit faster.
3) Resale of a known shops established product is likely to be easier - that said, forget about recouping your money... Warranty varies and falls in this category.
As far as the obvious mods, there seem to be two: first improve the power supply - doesn't seem to matter what kind of product it is, there is always room to make it quieter, stiffer and more stable. Second, change some combination of caps (coupling usually).
Have fun - the best advice I can give you is enjoy the process.
If you want to control costs and get a guaranteed outcome, the best bet is to go with an established "name" modder and mod a unit he already has experience with or has "productized".
There are three problems this helps to overcome:
1) Since most manufacturers don't put up their circuit diagrams etc, there can be a long period of discovery with a new unit as the modder figures out what the guy ahead of him did and didn't do - and why. That can get expensive
2) In theory, modding involves a certain amount of critical listening and fine tuning. When a modder does the same mod on an ongoing basis, you gain the benefit of his experience and evolution, as well as all the other owners feedback. This gets you a better unit faster.
3) Resale of a known shops established product is likely to be easier - that said, forget about recouping your money... Warranty varies and falls in this category.
As far as the obvious mods, there seem to be two: first improve the power supply - doesn't seem to matter what kind of product it is, there is always room to make it quieter, stiffer and more stable. Second, change some combination of caps (coupling usually).
Have fun - the best advice I can give you is enjoy the process.