While a number of people in the forum recommend 750Ti, after researching several issues, I tend to think it is not advisable to purchase any graphics cards at the moment, or rather to postpone buying them as long as possible because:
(1) It looks like Nvidia released 750Ti in a hasty manner without properly paying due attention to the design details because most 750Ti cards are equipped with non-PWM fans which make it almost impossible to finely control PWM fans of aftermarket coolers.
(2) Still worse, whether you venture into the risky realm of aftermarket coolers or not, at the time of writing, the fan section of ALL 750Ti BIOSes is not editable (without a single exception) unlike that of 660/760 cards, meaning that the minimun fan speed, though varying with different vendors, are around 900-1000 rpms, which are far from silence.
It strikes me that Nvidia intentionally released half-fledged cards as precursors to proper Maxwell-based cards to be released in 2015, only to timely deter the pontential dominance of AMD. I would personally recommend not to purchase any graphics card for the time being if you are not playing games right now.
In terms of supporting the latest NVIDIA cards NiBiTor never got much further than the GTX 560. So modifying the BIOS for NVidia 6xx cards has meant using something else, such as Kepler Bios Tweaker. I have downloaded the BIOS for a couple of 750Ti cards, the EVGA 02G-P4-3751-KR and the MSI N750Ti-2GD5/OC (the Gaming model) from the TechPowerUp VGA BIOS collection and tried them with the Kepler BIOS Tweaker. The good news is that the BIOS does seem to be editable. The bad news is that in both instances the settings under the Fan Control Range section are greyed out, so that adjusting fan speeds using a BIOS edit seems to be completely out with the 750Ti. I tried a third BIOS, the one for the Palit StormX Dual with the same result, no control over fan speeds.