need some upgrade advice!!

[Matson]

I have had this computer for a couple of years now and im looking to upgrade but not sure what i should upgrade that would give me the biggest performance boost. Should i go for one of the overclocked bundles from this site or a new graphics card or just a single part? Out of the parts i have at the moment which upgrade would give me the biggest performance increase.

My spec is:

i7 920 @ 3.8

Board: ASUSTeK Computer INC. P6T SE

8gb crucial 667mhz ram - overclocked

900watt psu

2 x ati 5870 cards in crossfire.

Any advice would be aprechiated.

 

[Matson]

I dont have an ssd, ill definatly check them out if you think it will be a big benefit for me. What would be the biggest benefit of putting the OS on one of those? just all round faster loading of programs and apps ect?