Need help upgrading my PC (Inexperienced) ~500$ GPU, PSU, etc.

[Turtlepanda]

Was looking at getting some upgrades for my desktop (Fall 2010). I am a civil engineering student so I want a computer capable of running autocad software as well as some gaming on the side (nothing too intensive: WoW, LoL, Skyrim,etc.). Currently have a budget of around ~500$ for upgrades. Was looking at some new video cards for my computer but was wondering if there was a more optimal upgrade. I have little experience in computer hardware so any input would be appreciated.

My current specs:
HP Pavilion Elite HPE 310T
Intel i5 750 quad (2.67ghz)
6gb DDR3 ram
Radeon HD 4850 1gb
300W PSU


Was looking at either a Radeon HD 7870 2GB, Radeon HD 7850 2GB, or GTX650 Ti Boost 2GB. In addition a Corsair Builder Series CX 600 Watt ATX/EPS 80 PLUS (CX600) to replace my current PSU. Do not actually know if these components will work in my current set up.

 

[manofchalk]

I would go for an upgrade like this.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

Video Card: MSI GeForce GTX 760 2GB Video Card ($254.98 @ SuperBiiz)
Case: Corsair C70 Gunmetal Black (Black) ATX Mid Tower Case ($79.99 @ Newegg)
Power Supply: XFX 550W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($45.99 @ NCIX US)
Total: $380.96
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-07-27 10:25 EDT-0400)

New case as I doubt your HP will have the sufficient airflow to handle the graphics card.

 

[Turtlepanda]

I would go for an upgrade like this.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

Video Card: MSI GeForce GTX 760 2GB Video Card ($254.98 @ SuperBiiz)
Case: Corsair C70 Gunmetal Black (Black) ATX Mid Tower Case ($79.99 @ Newegg)
Power Supply: XFX 550W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($45.99 @ NCIX US)
Total: $380.96
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-07-27 10:25 EDT-0400)

New case as I doubt your HP will have the sufficient airflow to handle the graphics card.

So in your opinion the RAM and processor in my current setup is fine? I am not looking for top of the line performance just some upgrades since the computer is about 3 years old now. In addition, would any new video card (150-250$ range is about what im looking at) most likely require a new case to promote better airflow?

 

[manofchalk]

The CPU is fine for now, but that would be your next upgrade in the future. RAM's fine, 6GB is enough for gaming though 8GB is typically recommended.

I would get a new case anyway TBH, the ones used by Dell/HP offer minimal airflow and are a bear to work with from what I hear.