I like just about everything, but I question you GPU choice. The native res on the the Dell is 1920x1200, correct? The 320 is going to have a hard time pushing games if you want to play at that res. If you don't mind playing at lower resolutions, the card will be fine. Otherwise take a look at the 640 version, or the GTX.
That GTS (Or any other GTS for that matter) is not going to push a 24" 1920x1200 display, your chances are as good as a snowball in hell. To push that kind of resolution and have an enjoyable, fluid gaming experience you'll need SLI GTX. If you want to have jumpy 20-40fps (especially in future titles), then a single GTX.
As far as PSU goes, that one is decent, however I prefer Corsair 520 or 620HX for single card setups and PC Power & Cooling Silencer 750 or Antec TruePower Quattros (Either 850 or 1000) for SLI/Crossfire setups.