ysmonyog, let me clarify thetype of graphics card 1st.. there are two types of graphics cards available, gaming Graphics card and workstation graphics card.
As the name suggests, gaming graphics cards are mainly developed for providing good gaming experience. But now a days lots of extra features have been added to these cards and they are now capable of improving the performance of lots of applications apart from gaming.
All the applications you've mentioned are actually going to be benefited even if you add a current generation gaming cards. These cards are available in all the ranges, from 2K to 40K
On the other hand, Workstation cards are designed to assist the development works and gaming is simply not possible of them. So if you add these kind of graphics card then obviously the performance boost will be huge but on the expense of gaming experience and I'm sure your son is not gonna like it. These cards are costly and you can't find a decent one at below 10K price tag.
So if you take my suggestion, I'll recommend you a modern generation gaming cards which will solve both the purpose. My suggestion will be Zotac GTX 460 1 GB @ 10K. The reason for suggesting an nVidia card is as CUDA is more mature and the number of softwares support nVidia's card is greater than that of ATI.