Since GTX650 is just an overclocked GT640 by specs, a GT640 is
approximately 50% faster than your GT440. It isn't enough of a performance increase to warranty requiring a change or upgrade in your CPU. But, GTX650 Ti has twice the specs and nets as much as an
80% improvement-- and this was done with a more recent processor, because the CPU runs the game and tells the GPU what to draw. Not that you won't see a gain, you'll definitely see a gain; but as long as you play GPU-intensive (single high-res display and high details) you should be fine.
Just to make sure, both 650/650 Ti require an external 6-pin power cable, or two available 4-pin molex using the included Y-adapter cable with the graphics card, unlike the GT440 which didn't need additional power. GT640 doesn't need additional power, so you could get that if your PSU didn't have extra cables, otherwise you will need a better PSU for the other cards.
The following is more of an FYI:
TDP is short for "
Thermal Dissipation Power", for CPU's it refers to a
heat category for multiple processors to qualify for the same OEM cooler type. It has absolutely nothing to do with the electrical consumption of the processor, and commonly incorrectly referred to as electrical draw. True TDP values will vary with frequency, cache, cores and the lithography (transistor size).
With regards to graphics cards, there is only two numbers of interest to anyone: Board power and System Power. Board power is actual usage, or rather the design load at reference frequencies. System power is defined as nVidia making up a configuration and adds the card and quotes the PSU used. Because nVidia does not tell us the specs of this system, the "System Power Requirement" wattage number is technically meaningless. It is only for liability; that if anything somehow goes wrong with the card and your PSU is less than recommended, you run the risk of losing warranty.
So despite the system requirement for GTX650 Ti being
400W and you're on the edge, because your parts aren't overclocked, you've got an overhead and you're fine with either card.
post edited by lehpron - 2012/10/12 23:54:55