Maximum PC

Hi all,

I'm currently using a pretty decent self-assembled gamer PC which I bought back in 2009. Right now, I'm thinking of either upgrading it or assembling a new one as the performance isn't the best anymore.

First, my current system:

Mainboard: Gigabyte P55A-UD3 Rev 1.0 IMO not the best one, buggy BIOS and bad arrangement of PCI x16 and SATA ports (cannot install a second GPU unless you sacrifice most of the SATA ports).
CPU: Intel i5 760 @2.8 GHz Really, really good one for the current state back then. Still very decent, I think.
RAM: 2x 2GB @1333 MHz
GPU: Sapphire Radeon 5870 OC Vapor-X I'm really content with this one, gets to the limits with Crysis 2 and Battlefield 3.
UPS: 650W, can serve up to 2x 6pin + 8pin PCI-E, have tried installing my friends CFX with two HD6970's which need exactly this config, worked.
OS: Win7 x64 Pro, not thinking of changing this ever.

So, my question is:

Is there any possible way I'm able to upgrade this current system to make it a bit more up-to-date without exchanging everything? Example:

- I buy a new GPU, say a HD7870 or 7970.
- For sure, I'm gonna buy more or even new RAM, 4GB is just a bit too few for today's use.

My thoughts on this are that if I need a new CPU, I'd need a new mainboard, most probably a new UPS plus a new GPU, which equals a whole new assembly without any of the parts from above.

Thanks in advance for any helpful answers, greetz polj