Dedicated physx Card and GTX 580

Even a 9800 GT would do fine as a PhysX card.

well i do want performance addons but i came to that it not really worth it a GTX 580 is a awsome card it blows everything out of the water so i think it bit over top to get another card for physx just lil more unnfff

How much power you need for a dedicated PhysX card depends on the game. I would have recommended two 570's over a single 580 with a dedicated physX card, but it sounds like you already have the 580.

I have used a 9800GT as a physX card and found it wasn't enough power for Sacred 2 PhysX. I know it's not enough for Dark Void (didn't get good rating anyways). It would be fine for Metro 2033. It would mostly be enough with Batman AA, but not as good as a 260.

A 450 seems like a reasonable choice, but if you had a chance to change that 580 into two 570's, I'd go that route instead.

450 makes a great physx card, for the price and will run physx fine for several years... heck i use my 450 as a gpu (damn student loans to pay off)

I know how you feel, got loads of debt to the federal government with no way out because of school.

oh i have a way out ... i'm just taking thier 25 year plan to pay it off and condensing it to 1.5 years... so i'm (sort of) broke but its cause i am planning on being out from under it in another 6 months, then i want my house paid off inanother 4 so 5 years out i owe nothign to anybody... i live liek i'm broke though to save money and work 3 jobs/run a small buisness of my own hopefully it'll be worth it in the end  

I've been using a GT 240 on a PCIe 4x lane, so it tops out at around 80% usage (bandwidth limited). Honestly I've never noticed framerate drops because of PhysX (as in framerates were pretty much the same with or without PhysX/or high vs low PhysX usage). I've played Mafia 2, Metro 2033, Batman, Mirror's Edge, and a bit of Dark Void.

So 9800GT is a tad faster than GT 240, but anyway all I'm saying is you REALLY don't need a lot. It mostly comes down to the core count AFAIK.

GT240: 96
GTS250: 128
GTS430: 96
GTS450: 192
9800GT:112

Of course the newer cards are faster generally due to new architecture. So, looking at this little list I'd say a GTS 430, GTS 250, GTS 450 are pretty good choices. 450 at the most.

edit: Well doing research is good. Just as a quick look I found this thread http://www.evga.com/forums/tm.aspx?m=768946&mpage=1

There's a post a little down and the guy writes:
"I get an average of 67fps with SLI GTX480s and letting them handle both 3D and PhysX and 96fps avg with the 8800GTS handling PhysX in this game." that 8800GTS has 96 stream processors.

I assume in Dark Void you don not set PhysX to it's highest setting. I've seen benchmarks showing it needed a 260 to top that one out, but it does depend on the game.

You know we never did ask, what GPU you had from your previous build (if any)?

This chart from Tom's Hardware is showing that a GTX 260 and above is best. Unfortunately, they don't test any 400 series cards for dedicated PhysX.
http://www.tomshardware.com/reviews/nvidia-physx-hack-a...

Nice motto, although I'm certain that my FPS was a constant 60FPS throught the game (1080p, max settings), with one notable exception of a "hideout" exploding causing huge lag. But the rest of the game was very smooth, and I'm only using a GT 240 as I said. I also have kept a very close eye on GPU usage via Afterburner and in the most intensive games it's rarely averaging more than 30-40% usage. Understandably then you'll see lower peak numbers but MOST of the time it won't make a big difference.

All that said, it does go to show that ~200 CUDA cores is going to deliver optimal performance. So GTX 260 or GTS 450.

Mafia 2 is the most PhysX intensive game available.

Naw, that title belongs to Dark Void. With PhysX set to low (not high): http://physxinfo.com/news/1657/dark-void-physx-benchmar...

I can't find any benchmarks with it set to high, but just to be able to set physX to high in that game, you must have a dedicated card or it won't let you.

EDIT: That benchmark does show one with PhysX set to low, medium and high with a 250 dedicated physX card. The high settings tanked with it.