basically any discrete card in the market is better than the intel hd3000 I would recommend and ati 6850 or nvidia 550 gt for that price range... but again if you want an improvement over the hd3000 you can buy a sub $100 card that can do the job
If you can find an extra $5 in your budget then you could get this card which would be light years ahead of the HD3000 and you would be set for quite sometime. You already have an outstanding cpu selection and this card would be a great compliment for it.
OpenCL runs with Nvidia also. I'm not sure what editing software he uses, but the kind I use does benefit from CUDA. Which is the only reason I don't own modded CF 6870s right now, and am waiting for the 600 series.
Yeah I think OpenCL should be the market standard when it comes to GPGPU. I can see it maturing into something great due to it's flexable nature. Oh and on my recommended card, try the SAPPHIRE 100283-3L Radeon HD 5770 1GB.
I've had many saffire cards w/o problems. It is at a great price point. I also like the EVEGA GTX 550 Ti mentioned by inzone above. Both cards have good performance, just the GTX is around $135 and the AMD around $105