Up grading power amp... Mono blocks or stereo amp?

The primary argument for monoblocks other than shorter speaker cables (which by itself is a pretty important thing) is that there are no shared power supplies. An amplifier that has separate internal power supplies will be described as 'dual mono', but most stereo power amps do have shared supplies. In most stereo amplifiers, the incentive is price, as the chassis is often the most expensive part, followed by the power transformers.

Conversely, monoblocks are usually built to a higher standard as cost plays less of a role.

Overall these are generalizations, but good to keep in mind when looking at a specific product. They often are helpful in guiding one to an audition, but the audition is really the bottom line.

Eldartford, in a power supply with plenty of capacitance the caps are only charging at the peak of the AC input from the wall. At this point the rectifiers turn on and off (commutate) only at the peaks. So you have a spike that is riding on the top of the AC waveform from the wall.

Double the current and the spike is bigger- more noise will be present in the power transformer core. In addition, power drawn from one channel can lower the output voltage of the power transformer secondaries due to the internal DC resistance. This can affect the other channel (slightly). If *both* channels are drawing a lot of current, the voltage sags more. Its not a bum rap, its just what is.

A designer of a stereo amp has to consider these things. Its not really a problem in a monoblock.