GTX 260 with Radeon 4670 on Windows7 for CUDA development? Preventing video driver conflicts

I’m going to get an EVGA GTX 260 for my first CUDA attempts (216 cores). I want to put it in my Core i5-750 system which has an ATI Radeon 4670 as its primary video card. I thought it would be cool to leave the Radeon in and therefore use the GTX 260 strictly as a GPGPU tool. My concern is that I set things up properly so that the the two cards can coexist and that the GTX 260 absolutely does not try to do any video display tasks. I’ll be using Windows 7/64-bit which claims to be able to support graphics drivers from different manufacturers being co-resident and I’m not sure if that will be a blessing or a curse. My other concern is that I don’t do anything to make the GTX 260 unavailable for CUDA access since I worry that the drivers involved with video display may also be responsible for servicing CUDA calls and I might do something accidentally to turn off the CUDA service.

If anyone has any tips for this scenario I’d like to hear them before I potentially botch my system. Also, I’m using a 700 Watt ModXStream power supply. Will that be enough for the two cards? I ran the Antec power calculator on the system’s components and it came out around 420 Watts. That’s somewhat above the recommended 50% utilization mark but I’m wondering if that matters significantly in this case. The only other items in the system are 4 GB of memory, a 250 GB hard drive, and some fans.