Your current machine is a bit behind the times now, the processor, graphics card and memory have all been superceded by improved technology. Personally I would buy a new motherboard, a better graphics card and use DDR3 memory. You could re-use the case, DVD ROM etc. maybe the power supply depending on what new graphics card you get and you might want to increase the hard drive, or just add a second one to your existing drive.
Hands-on: Acer Predator Triton 700 review