can you fit a more powerful psu in that Dell? that would give you more options on a gpu and geek is right, a 4350 is not much better than what you have
DELL is well known for using propreitary power supplies much like HP epecially with their low profile systems.
For power and likely thermal the 4350 will work just fine but making sure there are plenty of air flow in the case will greatly help if there are any thermal issues. You can also try a more modern card like a 5450 with that unit.