Hi Vasu,
Crabtree plugs are good. Wherever I have used them, I am very satisfied. Do you also use the sockets from Crabtree? That would provide perfect contact. Can't say much about IEC connectors.
An online UPS with isolation transformer giving out sinusoidal voltage would indeed be very expensive. You live in the New Alipore area. Cranky who is also a resident of that locality tells me that there is not so much voltage fluctuation. Living in Salt Lake, I find that very difficult to absorb. You guys must be very lucky.
Regarding your experiences with power conditioners, I am not so sure. See, whatever outlet you are drawing the power from it has a circuit size, and under no circumstances cannot exceed that and then would trip. So if you have a conditioner with enough support on wattage, it should really not matter in audio quality. My need is no more than 1 KVA at a given point of time, and I have 3 KVA a Krykard servo stab (from Chennai, and not cheap at 13K). I plan to add a Ultra Isolation Transformer in the chain (after the servo) at a later stage.
I draw the power from a single 15A socket into the servo stab. From the servo stab, it goes to a home made power distribution box which powers all equipments. All plugs and sockets are from Crabtree. Cables are 3 core Finolex and Havells (each of the core is 4 sq mm) and inside the box the cables are 2.5 sq mm. In the box, it is a star configuration, that is, cables go to all the connecting sockets from a single point where the power cable from the servo ends.
Also, as stressed above, one should draw the power for all equipments (to be used together) from a single wall power socket. I am given to understand it is important,
Regards.