The bottom line...
After a week reading Psu Ratings and Specs, calculating what max watts under low/full load i should need for my system & components to run smooth and not being overkill in the choice of a too high voltage rated PSU.
I arrived to decide and choosed a full oem semi-modular 700w 80+ Gold (87,5%-93%) efficiency under 20% to 50% load. Is a Dual-GPU ready certified Psu list for my graphics & with c6 support, ErP 6 Ready.
Which was also better rated and efficient than a value one 650w 80+ Platinum.
Backed up my cheapest GX 650w v2 in the cupboard. It'll serve me only in case not being stuck!
Why 700w instead of 750w?
The reason is quite simple.
-I'm not planning upgrading in a few years my mains components and i surely will add some peripherals but they will not change too much in the PSU power consumption.
-The Psu will be efficient & economic for my bill only if i can use it at the right load, so i far prefer lower watts and better efficient states under loads.
-700watts (58A) is far what i need and i'll not reach the peak load more than a second, anyway!!
-The Psu is enough branded to.
This was just not an easy task!