which graphic card serie Workstation or Gaming?

Hello all,

I have been comparing the two ATI series also the
equivalent NVidia and can not figure out what are
the major differences between the Workstation
and Gaming series?

One main difference is obvious: price tag

I have a DELL Worstation 670 with 64-bit extensions
and PCI-Express graphic port and would like to upgrade
it with the most powerful and reasonably priced Graphic
Card but I am affraid of selecting the cheaper Gaming
models serie and then realizing it would not perform
as well as the Workstation model ...

My needs?

- Software Development
- Database Development
- Gaming :-) Half-Life 2/Counter-Strike/AOM/etc
- No CAD applications
- Support for different OS(s): XP, Linux, Unix, Solaris 4 Intel.

My Workstation shipped bundled with an ATI Fire V3100 I
did not want to ask DELL for a different one because they
would most likely overprice it, I decided to get the cheapest
bundled from DELL and upgrade later on.

TIA,
Best Regards,
Giovanni