Amperage 2 vs 4 channels amplifier

I would ignore those specs altogether. Amplifier current ratings are among the most useless of specs, IMO, as they almost always represent how much current the amplifier (or in some cases just its power supply by itself) can supply into a dead short (zero ohms) for an unspecified tiny fraction of a second. Consider the following:

60 amperes into 2 ohms corresponds to 7200 watts
60 amperes into 4 ohms corresponds to 14400 watts
60 amperes into 8 ohms corresponds to 28800 watts
120 amperes into 2 ohms corresponds to 28800 watts
120 amperes into 4 ohms corresponds to 57600 watts
120 amperes into 8 ohms corresponds to 115200 watts

So obviously those amounts of current are never supplied into real-world speakers.

For further discussion of this see the following thread:

https://forum.audiogon.com/discussions/current-limit-onset-definition

Regards,
-- Al

What Al said: ignore.

Although an amplifier max current rating doesn't represent anything useful, however, if two amplifier both rated 100watt/channel, one max current rated 50A and the other one rated 30A, we can assume that the 50A rated one has a beefier power supply.

Max current represents how beefy the output stages are but it does not  mean the power supply could handle more than 1 channel doing this at once. It's' just a measure if the amps ability to handle difficult loads. Bragging rights, if you will.

Also keep in mind for HT, the center channel has most of the output, surrounds have the least, especially if following the THX model of crossing them all over at 80 Hz. 

@imhififan
Not necessarily, especially if the amps being compared are from different manufacturers, because (using your example) the amount of time the 50 amperes and 30 amperes can be supplied for is not usually specified. For example, the 50 amperes may be suppliable into zero ohms for only 10 milliseconds, while the 30 amperes may be suppliable into zero ohms for 25 milliseconds.

Also, the amount of current that can be supplied into zero ohms for these brief amounts of time may be limited by the output impedance of the particular amp, which is unrelated to the power supply.

So generally speaking I don’t think these specs can be used as an indicator of power supply "beefiness," or of anything else for that matter.

Best regards,
-- Al