My new build will be arriving soon, and I plan to game on it. Should I install Ubuntu and Wine for windows games while Steam moves over to Linux? Or should I install Windows 7 and switch to Ubuntu later? or should I do a dual boot?
Dual boot. No OS has more titles available than Windows, if you game you're going to want Windows, driver support is also better. DirectX completely absent in Linux. You may want to just go windows only since your 128gb SSD is a bit small for multiple OSes (you can do it though it may get tight if you install games to the SSD).
The above advice is totally right - dual boot and game in Windows. As for what drive to put Linux on, could you re-use an on hard disk to install it on? You can also game a little on Linux without WINE on open source games. There's not much but Nexuiz and Blob Wars are good fun :-)
Also, I'd recommend Bodhi, Xubuntu, or Kubuntu over Ubuntu. The latter two are official variants that give you the benefits of Ubuntu without the controversial Unity UI. Xfce and KDE are (in my opinion) much sexier interfaces and far more customisable. Bodhi is awesome too and also Ubuntu-based so you have access to those same repositories for installing software from.