Kasakato said:
...Power supplies are really cheap these days. Some are less than $30 for 450w. And replacing them is easy. Just take out the screws at the back, and unplug any cables to the motherboard, cds, floppy. And put the new one back in just like you took it out....
I am sure this is well meant advice - with possible catastrophic consequences though. DELL is one of the manufacturers that used proprietary PSUs for their PCs - meaning they didnt comply with the ATX standards. If you replaced those with a regular PSU - you could kiss your PC and most components in it good by.
Thankfully you posted your PCs specs and seeing its a newer machine you'd be safe to replace it with a regular ATX PSU. A good brand name economy PSU is the Thermaltake 420W on newegg - it usually goes for around 35$.
Defenitely stay away from anything cheap !!! Big no no for PSUs.
If you decide to replace it i'd measure your existing one first - and compare it to whatever you are going to get - just to make sure.
Now to the card itself - you should be able to get away with a R9600 or better 9600Pro with your current PSU. They go for around 70$.
For better performance a 9800Pro would be ok (100$) - but you might end up replacing the PSU.
Other good cards would be Nvidia 6200 (non TC) or 6600. For ALL cards make sure they have at least 128bit memory bandwidth - anything lower and you take a huge performance hit. If you buy a 6200 you need to get a 256Mb version to have 128bit memory bandwidth.
All these things mentioned your best bet (performance/ price ratio) would probably be the Nvidia 6200 - for around 70$ you get much better performance than the equally priced R9600Pro (or even more expensive 9800(pro)).
Whatever card you end up getting - make sure you follow proper deinstallation/ installation instructions to ensure the drivers work correctly.