No benefit from a 2nd dedicated card with the 200 series as they have CUDA 3.0.....with G92 and G80 yes but not with your 260, you would be just wasting your money.
I was just wondering since there are lot of these PhysX cards floating around on trade boards for cheap.
I've been overclocking my GTX a bit today and I have pushed it to 729/1458 core/shader with VRAM at stock. VRAM is easy to damage and nearly impossible to repair/replace aside from RMA'ing the whole card so I decided to leave it alone. This card has plenty of bandwidth already and if it's anything like my old X850XT or 8800GTX then VRAM overclocks won't do much performance-wise. (With my old X850XT for every 10% I overclocked the VRAM I only gained 1.5% in benchmarks, or less. 8800GTX did little better.)
Actually, I set my GTX clocks to 720/1450, but it corrected itself to 729/1458. Anyways, 729MHz comes to 26.5% overclock on the core compared to stock. My temperatures haven't risen by much under load vs. stock clocks. (about 2C higher)