Agree with Johnhifi, but like to add that the prescribed breaker per code is meant to protect the correct sized WIRING that comes after it, from overheating and possibly causing a fire. An equipment failure current might not be high enough to tripout a 30A or even 20A cb unless there is a direct shortcircuit or something near that to be detected and act upon by the cb.
Simply put an UNPROTECTED equipment could well continue to FRY as long as the said wiring and the supplying cb can happily supply the current. So its very important to note that the correct fuse rating at the back of the equipment is the sole protection against such disaster happening, and should never be replaced with a higher rating. However to prevent frequent nuisance fuse blowoff, especially for power transformer turn-on surge so typical of our audio equipment, some maker do specify a T type fuse which delay a fraction before blow off, compared to the quick blow F (general purpose) type fuse of a same current rating.
Timo, I think its okay even to use a arc welder-sized input wiring as long as the equipment's FUSE PROTECTION are correctly in place. A 30A wiring compared to 20A will have less voltage variation seen at equipment power input plug between low and full demand. But how does all this affect the SOUND?
To each his own preference where he wants to upgrade first. My own experience in more Copper "investment" upfront resulted in a bigger sounding, less hesitant, more lively sound compared to that previously. Of course I also have in place all the other gears like powerdistributor/filter, powercords etc. This effect is evident even for my 28W/ch SET amp! What about those considerably much higher powered Audiogoners gears. Try figure that out.