Any decent plug will do, but perhaps the tolerances might be better on a higher-premum brand. I'd be content to use Anchor. MK is an international brand, but I have my doubts (due to experiences as per my comments on your other thread) that the quality of the stuff they make/sell in India is as good as elsewhere. Just ask in your local electrical shops: the better ones will stock MK.
Polarity and the three-pin plug: the "dummy" earth pin ensures that the left pin always goes to the left hole, and the right pin to the right hole. With a 2-pin socket, the polarity is unknown.
One other thing you can, maybe should, check is the polarity of the socket. It is far from unknown for them to be wired wrong. However, if you are unused to this work, please get an electrician to do it for you. This is for the safety of your equipment, but most important is the safety of you!
Do not put off listening to your amplifier just because you can't find an ideal brand of plug. Any plug will get you going. If you have major problems like you mentioned before, this is not plug-induced: you should look elsewhere for the cause.
PS... I'd prefer 15-amp, but there are other issues. You should not change a 6-amp socket to a 15-amp socket if the cabling is not heavy enough to carry that load. Basic safety issue.
PPS... I am not an electrician --- I just picked up the practical basics along the way.