You can't compare a 7750 to a 750TI because the 750TI renders three times faster. Games that will run on the Nvidia would shurely have to be drilled down to get similar frame rates on a 7750.
I have never said that the 7750 can be compared to 750 Ti (I own a 750 Ti). I specifically said that the 7750 is an "aging" card.
The 7750 is a good low profile card but quite old and so not powerful enough compared to the 750 Ti.
It's just that I cannot stand the KFA2 GTX 750 Ti noise, and I don't think that Nvidia is interested in developing its own zerocore.
So for the time being, I cannot find anything better than the 7750.
Point is: Low profile cooler have a hard time coping with load temps, will need fast spinning tiny fans. They also have not enough cooling surface, so semi passiv is mostly ruled out.
If you want near 0 DB at long or short or whatever idle, just hybernate your system or suspend to disk.
As soon as internal graphics isn't fast enough you have to start making compromises. Gaming and always on is not optimal. Gaming and silent is difficult. One way is to break it up into several systems. Otherwise you need to compromise. Dropping the low profile requirement seems reasonable to me.
It seems that you are all too focus on power consumption during gaming.
If implemented correctly, if the display is off the card has absolutely nothing to do and should have a very low power consumption (< 4W).
A low profile double slot graphic card should have enough cooling surface to dissipate 4W without turning the fan. This is exactly what AMD is doing with its zerocore technology.
The HD 7750 has similar power consumption profile (but different efficiency) than the GTX 750 Ti (15W at normal idle, 60W when under load). And AMD has managed to shut down the fan during long idle (i.e. when the display is off), so I don't see why it is physically impossible to do the same thing with the GTX 750 Ti.
Given the hard facts, there can be only 2 options :
1) AMD is lying and zerocore doesn't work well enough on a low profile 7750 to stop the fan during long idle (i.e. display off). Won't be the first time that a big corporation is overselling a feature.
2) zerocore is working well enought to stop the fan of a 60W TDP low profile graphic card during long idle. If we don't see it in Nvidia current graphic cards it is because people are not really interested in this feature so Nvidia has no real incentive in developing it.
If I buy the low profile HD 7750, I will report here if the fan can be stopped at long idle.
If I buy the AMD next gen low profile (which should go out in 6 months-2 years), it should have the zerocore feature and I will report if it works or not.
As for Nvidia, they are not really interested in power consumption during long idle (even for normal sized card) so I don't think that I will go with a Nvidia card (shame because the reference GTX 750 was reported to have a power consumption lower than 6W at normal idle !).
Now, as I have yet to see one single people (including me) in this topic who really has tried the zerocore feature before giving theory on what is possible or not possible for stopping the fan at long idle on a low profile card with 60W TDP, I propose to stop the discussion here as it is useless.