Upgrade or build a new gaming PC?

Hi guys. Finally, after a good long run of 5 years of gaming without problems, I've encountered for the very first time this year that I could not run a game because I do not meet the minimum requirements. That would be Planetside 2, then Metro franchise, and recently, could only play Rome 2 Total on minimal settings and still experience lagfest.

Now... here's where that question comes from. Shall I upgrade my current PC or start from the scratch?

Here are my specs from a Dell XPS 420. 

CPU: Intel(R) Core(TM)2 Quad CPU Q8200 @ 2.33GHz

RAM: 8 GB 

GPU: ATI Radeon HD 3800 Series (3875 or 3880? Not sure)

OS: Windows Vista 64 bit

Motherboard: ACPI x64-based PC (Idk? Not sure how to find this out.)

Ok, I think that's all the specs you guys need to know. However, I have a question regarding to the motherboard and the ram. How do you exactly find out what kind of ram is installed into your computer and what motherboard you have?  I just looked up in the Device Manager and not sure where to look in there. 

If it's a dell chances are you'd need a new power supply to run a new graphics card, and you might need a new case depending on size requirements.

I would suggest building a new PC. That PC will still be fine for non gaming stuff though, so you could try selling it or giving it to a friend/family member.

Start from scratch. You couldn't do much with the Dell.