Better.
From the pics I've found the case looks to be a 'mid tower' so at least it's not a slimline-which would be bad.
Bad new is that OEM power supplies are notoriously weak so I'll make several suggestions:
1 the HD7750/GTX650. Weakest but cheapest option. Check the specs, some use DDR3 memory, look for those that use DDR5 instead. Most GTX650s don't need an external PSU lead to run, some do, so again, check the specs, either card will run off the existing PSU if the card does not require an external PCI-E power lead.
2 HD7850/GTX650Ti Boost. A good deal faster, and more expensive, either will need a new PSU to run. Probably the best match for your budget and system.
3 HD7950/GTX760/GTX660Ti top line, VERY fast, only consider if: You're running a 1080 monitor and want some serious eye candy and you can extend the budget a little, again, they'll need another PSU to run.
For options 2 and 3 I'll suggest that you look for a 500-550Watt PSU with dual 6+2 pin PCI-E leads, there's not much price difference between this spec and something weaker.
Look for: Antec, OCZ, FSP, XFX, Seasonic, Silverstone or Corsair made units and AVOID cheap PSUs, they're cheap for several bad reasons.
Nice places to shop (amongst others) : Dabs, Overclockers, Scan, CCL, Novatech, Microdirect, Ebuyer, Pixmania and Aria.
And, as Columbo would often say: "one last thing, Sir.", get the tape measure out and check what you want will fit. It's been done plenty of times before.