Dell Dimension e520, Intel Core 2 6300 1.86 GHz 1.86 GHz (it's listed twice),
1 GB RAM, and my graphics card is a NVIDIA GeForce 8600 GT.
You'll be fine with that system for Evolution. The fact that you said you could play Dead Space decently (as in, hardly any slowdowns) was already enough to know that Evolution would work well for you.
I last upgraded my system 3 years ago, and it can play both Dead Space and Bioshock with ease. Since Bioshock uses the same Unreal engine as Evolution, and it's considered a fairly demanding game, I know I'll be able to run Evolution as well. (Though I would still like to upgrade again at some point in the not too distant future.)
Do you know if this chip can play those games, the nvidia geforce 6150se chip? I've looked around on this chip and it's not good news for it. :/
Will you be able to run those games with that video chip? Yes. But will you be able to run those games with acceptable performance? I'm afraid not. They will run very, very slowly and be almost unplayable.
If you'd be willing to invest $70 in a new video card like the Radeon 5570 and plug it in (as long as your computer has one or more PCI-E slots, that is), then you'd be able to play Evolution and a lot of other games with decent performance. Although all the components in a computer affect how well a game plays, the video card is the single most important part in getting games to play well.