What would you upgrade in this system?

[Levirginien]

I would not call myself a gamer, but Speed is essential and I always want my PC to be very responsive. My current rig includes the following:

Processor: E 6700 (@ 3.6 )
Motherboard: Asus P5K Deluxe
Memory:Corsair 4GB DDR2 XMS2 Dominator PC2-8500C5 TwinX (2x2GB)
Graphics Card: NVIDIA 7900GS
Hard Drive(s): SAMSUNG HD753LJ (750 GB, 7200 RPM, SATA-II)
SAMSUNG HD502IJ (500 GB, 7200 RPM, SATA-II)
Optical Drive(s): TSSTcorp CDDVDW SH-S203D
Cooling: Zalman 9700 LED
Case: Antec 900
Power Supply: JANTEC 700 Modular PSU
Monitor(s): Dell ultrasharp 2408WFP
Operating System: Vista Ultimate 64 SP1

What would you upgrade to improve overall system performance

 

[Levirginien]

Thanks everyone for your superb contribution. I thought about upgrading the graphic card to a 4870 but I read that It won't make any difference since I am not a gamer...I use my PC mainly for photos, music, general office work, internet and films.