i too WAS a TX650v2 owner. i am like you OP, in that i absolutely must have a quiet rig, and the TX650v2 definitely didn't cut it for me. i was actually quite surprised, considering its a modified and rebadged SeaSonic unit. i guess the fan must be one of the modifications, or at the very least the fan speed controller. while i never had any software installed that gave me a PSU fan speed reading (and thus can't confirm whether it was idling at 1700rpm), it was easily the loudest component in the system. but even though i couldn't confirm its fan speed, i'm reasonably certain that it was working as it should have. that same computer now uses a SeaSonic SII12 620, and its fan doesn't even spin at idle. under the same ~400W load, the fan spins, but so slowly that its completely inaudible...add to that the fact that there's no coil whine or any other strange component noises, and this thing is DEAD silent.
in its defense, i will say this - the TX650v2 was no louder under load than it was at idle...and i had it pretty well loaded with a 6-core CPU crunching an assortment of DC projects, and a 5870 GPU crunching Milkyway@Home and SETI@Home 24/7 (for a ~400W draw). that being said, it was ultimately too loud for me. like the OP said, sound is subjective, so if i had to vaguely quantify it, i' say that the TX650v2 isn't loud at all as far as PSU's go. but it is far from silent.
i have a SeaSonic X650 in another rig which is almost as quiet as the SII12 620 in my other rig...suffice it to say its silent as far as PSU's go. Corsair sells an AX650, which is a slightly modified and rebadged X650, but its a bit more expensive than the X650. i've never used one, so i don't know if the fan or the fan speed controller is one of Corsair's modifications to this unit or not.