what is Nvidia physx & cuda??

Physx is a GPU assisted physics and particle effects engine. Some games have an option to run Physx which adds some
more effects but they really aren't worth it. Also some games can run Physx on the CPU without a NVidia card
but somewhat slow

CUDA is for GPGPU. It is only used in a few programs (not games) and AMD cards can use OpenCL for GPGPU

Quick followup...

For lots more info about CUDA issues with AE, see:

http://forums.creativecow.net/thread/2/1019120

Look for my longer posts in which I cover various aspects of AE performance.

For an example of what one can build with used parts, see the feedback for a system I built recently.

Also, if you want to work with AE, you need a good CPU, but lots of RAM is more important. 8GB is
not enough. 16GB is baseline, 32GB preferred, 64GB if you can afford it (6-core systems). AE uses
a lot of RAM. Friend of mine had an AE scene which would grab 40GB RAM when it was rendered.

And again important, use a dedicated SSD for the AE cache. Lots of used units on eBay
can help cut costs here. For another system I built recently, I fitted a used 512GB Vector,
which as a high IOPS model is ideal. I also fitted a 128GB Sandisk Extreme II as a dedicated
Windows paging file (system had 64GB RAM, so the default paging file is 96GB), which
reduces the paging load on the C-drive too (Samsung 840 250GB used for the C-drive).

AE can hammer your entire system. Basically the performance will kinda suck if you just
use a generic system with medium RAM, no SSD and only a medium GPU which doesn't
have CUDA. Hence, don't use 'value' SSDs like the MX100, get something decent if you
can. 840 EVO, 840 Pro, 850 Pro or Sandisk X210 for the C-drive, any quality high-IOPS
model for the AE cache, something average for the paging file (another X210/128GB
would be ok), etc. For normal storage, don't use cheap SATA (avoid the eco green sort
of stuff). WD Black would be ok, but I keep hunting for Enterprise SATA being sold of
new as normal auction, eg. Seagate models that end with NS in the model name, or
various Hitachi drives such as the 7K4000 2TB (model HUS724020ALE640), eg. see eBay
item 151354498035 which I won recently for an excellent price).

Feel free to PM me if you have any detailed questions, happy to help.

Ian.

That depends on the game, the settings you want, your PC platform (ie. CPU power - some
games need good CPU performance), etc. A newer card is better for gaming, eg. a GTX 780
is about 2X faster than a GTX 580 for gaming. If I had the budget and was building a gaming
machine, I'd go for either a 290X or a 780Ti, though again after working with two 7970s this
week, I still get weird issues with AMD's drivers (refused to set DVI-out at 2560x1440, locked
up GPU-Z, etc.). Thus, given your desire for AE performance aswell, the best solution would
be just to get a single 780 Ti. Good for AE, good for gaming, and it does have the added bonus
of being much quieter than two 580s (uses less power too, so less heat, etc.) Plus of course,
you'd have the option later to add a 2nd 780 Ti for SLI if you wanted a boost to gaming speed,
AE speed, or both.

Check the Adobe site for exactly how CUDA accelertation helps (RayTrace3D function, Fast Draft,
various other things). It does not affect Classic3D render speed as that's done by the main CPU only.

To summarise: various AMD GPUs are good for gaming, but they will not help AE performance.
Various NVIDIA GPUs are also good for gaming, and they will help for AE. Thus, go NVIDIA.
If you can afford it, get a 780 Ti. If you can't, and even a 780 is beyond your budget, then get
two used GTX 580 3GB cards (though even 1.5GB models are still pretty good), top-end models
if possible that have better/quieter coolers such as the MSI Lightning Xtreme. NB: beyond a
certain point though, the amounts people are willing to pay for the better used cards is such
that you'd be better off just getting a new 780 or 780 Ti instead. It's the reference 1.5GB 580s
that can be dirt cheap, but then they make more noise (strictly for gaming only, a used 7970
would be better than a 580, assuming you don't mind the higher chance of driver issues).

Re the 780, I don't think the performance drop is worth the price difference vs. the 780 Ti.
I'd rather get a maxed out 700 series, giving the maximum possible SLI option in the future.
All depends on your budget though I guess. As I say, mine was limited, so I bought four
used top-end 3GB 580s, faster than two Titan Blacks for AE acceleration, at a fraction of
the cost. I've actually obtained 6 in all, obtained another two so that I could do general
3D benchmarking, etc., without having to pull apart the main system.

Ian.

Anytime.

Ian.