My current motherboard will support up to 16GB of DDR2 memory. Problem is that DDR2 is wildly expensive now compared to DDR3. The AMD Phenom II X6 1075T is actually an AM3 processor, so in a suitable motherboard (like
this) it can use DDR3 memory (up to 1333MHz).
Im now thinking that a simple motherboard upgrade (to that linked above) together with 4x8GB of DDR3 1333MHz RAM and a SATA3 hard drive might be the way forward. Will also mean that I can use the surplus funds to upgrade my wife's PC (which is more gaming orientated).