Socket A? Must be quite old Class D tech also, many folks bang on about inefficiency so we give them good Class-D now
Well, the most space on the board is taken up by a 2200uF/25V capacitor. The amp is based on a chip (the chip is under a heatsink, so I do not remember which one) and is available from China on ebay.
It does not seem to have any output filters, so while it sounds OK, I don't turn it on wen I am listening to FM radio.
As for the efficiency - to me efficiency matters the most on battery powered devices (unless the device is big and can have a big battery), it also matters a bit on high power devices that I keep on 24/7, but for something like an amp I'd rather have higher quality (or a tube amp, even if the sound was the same, tubes are cool).