If you want to stick with nVidia, then the best card would be another GT 440 because nVidia card have pretty high power requirements.
Here's the max power consumption from the same review as above:
CUDA and 3D vision are simply not going to work on a 300W PSU, so I would not jump on the nVidia train for those reasons unless investing in a much larger PSU ($75) and a much larger GPU ($200+). Just look for the most performance per watt, and take what is available.
The 7750 is the fastest with the lowest power consumption and would work well with a 300w psu but above budget. The 6670 is the fastest in that price range dollars that will run on a 300w psu
Ahh... I missed the $70 budget.
Okay, the best option is the Radeon HD 6670.
CUDA and 3D vision will not go well with lower Nvidia cards (same analogy for Physx). It is possible but not optimal. Unless you're really planning to buy a 3d kit which is obviously more expensive than your card.
For 3d and.such the budget will have to increase by alot. For 3d id recommend a sli setup and physx an accompanied gt240 with another higher end card. So you see wine taste on a beer budget doesnt work in this situation A 6670 is best for the price on that psu that you can do with your budget
I agree with the 6670 is your best option for what you want to do.