Whenever I buy a new computer or upgrade, I just check to see what is the latest nVidia OpenGL card and go with a model that is 1 or 2 steps less expensive than their best. Many 3D professional geeks consider the nVidia line to be the gold standard; the key being 3D professionals. That means they care if the card will run for days / stay cool / look great on screen / update drivers regularly / etc. The new K-series are excellent with their CUDA-GPU co-processors; these can do real-time viewport rendering which is a huge boost to visualize a final render.
The top-of-the-line cards are usually overkill for me, so I recently bought the K4000 which works great on 2x27 in monitors. If I were upgrading an older computer (or making a cheaper workstation) I would have bought the K600.
As Holo wisely advised (several times!) gaming cards are fine, but they’re not what the professionals use. I used to think it didn’t make a difference until I did a test. I opened up a huge file on two identical computers. The gaming card gave me lags and jerks every time I did a zoom / pan / rotate. The OpenGL card was fast and smooth. Case closed.