2. If some products/manufacturers have more issues & some others less. Which ones to avoid & which ones are recommended? /QUOTE]
Avoid: Anything Acudeftechguy buys from ecost.
3. I would require a step down converter (220 to 110, 50Hz to 60 Hz) & supply regulator (We face inconsistent voltages with significant drops & raises from time to time).
Definitely don't purchase from america then. I don't suggest doing the step down conversion for an AVR. The supply regulator is probably a good idea.
Do AVR's make a difference in what it sounds?
Most of the time, with the regular, quality brands (Harman/Kardon, Denon, Yamaha, Marantz, Emotiva, NAD, Parasound, Integra, etc) any difference there might be in its sound would be extremely, extremely subtle to the point where it's more than likely inaudible. If your amps are underpowered (especially when driving complex phase angles and extreme impedance dips) or the output impedance is high, then yes, you can hear a difference (especially on dynamic content like bass). I can't really comment on Pioneer, Sherwood or Onkyo receivers because i'm irrational but I bet they sound the same too. I just can't say with sureness.
I'd steer clear of anything with vacuum tubes, or anything from Sony, Panasonic, Samsung. I'm somewhat unconvinced of the truly entry level receivers' ability to drive real loudspeaker loads properly even from real companies listed above.
Normally I'd recommend the receivers with an MSRP around 900-1k because they're bound to have robust amp sections, reliable pre-out sections, as well as superior features(like Audessey MultEQ XT). It sounds like you're in a bit of a predicament though due to where you're located.
You guys convinced me (and am thankful), that speakers make the
biggest difference
*the speakers and their interaction with the room and listening position