Should I upgrade yet?

Current System:
PSU: Antec TruePower 650
Mobo: EVGA LGA 775 NVIDIA nForce 680i LT
CPU: Intel Core 2 Duo E6600
Video: EVGA GTS 450
Memory: 6gigs ddr2 800 (corsair xms series)
Several mechanical hard drives.

I don’t game a whole lot but I am looking to increase my performance in general. As you can see by my mobo/cpu combo I have been trucking along for 5 years or so. The video card is "newer" and it handles my graphic needs just fine and that can always be upgraded in the future more easily than the other parts, but I feel I’m due for a new mobo/cpu/memory. Is now a good time to upgrade to something that could last me another 5 years? or should I hold off?

To be honest the computer is still running great. I get more than acceptable frame rates in the few games I do play (wow, diablo, occasional first person). It just feels so sluggish when I’m working with my extensive eBook and music libraries.

Maybe i should get an SSD and see where that leads me, even if my mobo restricts me to sataII and my collections of music and books wouldn’t even remotely fit on one.

Anyone feel like sharing their educated wisdom with this bumbling fool?