The GX660r is quite upgradeable for its age. Seems odd saying that, but hey things move on soo quick
For all round performance, go and buy a 920xm CPU, its an extreme CPU which means all four cores are unlocked, so you can use a program called throttle stop to overclock all four core simultaneously, for the extra cost per clock the 940xm isnt worth the extra cash when the 920xm will overclock fine.
My cpu has all four cores overclocked to 22x133 (2.926Ghz) for its gaming profile, and stock speeds for other stuff.
Cpu came from ebay:
http://www.ebay.co.uk/itm/INTEL-i7-...0?pt=UK_Motherboards_CPUs&hash=item1e71e9b4e0
I got a Dell Alienware PSU from the bay, its an extact fit, 180W, and from France there are no import costs:
http://www.ebay.co.uk/itm/GENUINE-O...C_Portables_Cartes_PCMCIA&hash=item4abb143c2d
Other than that, performance wise, just stick an SSD in one of the drive bays, or increase the memory. There is a bios available to run xmp memory, but the ram I bought (2nd hand) must have been faulty, cos it broke the stability. So memory wise I'm running with the stock 6GB
And as mentioned above the GPU can be upgraded and overclocked, I have my 6970m underclocked and undervolted at 100x150 @ 0.8v for desktop stuff, and overclocked and overvolted to 800x900 @ 1.1v
Its all a balance to keep a reign on the temps while getting the performance, and not sacrificing any stability
Mick