You should be able to run all of those at a decent framerate.
I can run GMod and CS: GO + Source at 30FPS, though I have a bad PC at the moment. Partly the reason why I'm building a gaming rig.
Windows 7 Ultimate x64
Intel Pentium D CPU @2.80GHz || Dual-Core
3GB DDR2 RAM
ATI Radeon X300 w/ 128MB vRAM & Pixel/Vertex Shader 2.0
I also have a Xbox 360 HDD in my tower, had it lying around and wanted a use for it. (Hitachi 250GB HDD)
If you're still unsure, Google "Can I Run It" and you'll see a website called systemrequirementslab.com or something like that. It'll scan your PC and tell you whether you can run it or not.