According to the US Apple Store (click the Quad model, then look at the list of customizable features) the default memory is "512MB 533 DDR2 Non ECC SDRAM- 2x256".
According to the US Apple site, specifically the
tech specs part of the PowerMac section:
Quote:
|
PC2-4200 DDR2 SDRAM (NECC) installed in pairs: 512MB, 1GB, 2GB, 4GB, 8GB, or 16GB; 1GB or more available in choice of ECC or NECC
|
and
Quote:
|
Eight DIMM slots supporting up to 16GB of main memory
|
It doesn't look like there's any need to throw away the original memory unless it's either bad or you run out of slots.
EDIT: Oh, and purchase any extra memory from a third party. I assume the situation is the same in the UK as here in the States: Apple charges a lot more for memory from their store compared to other online/brick-and-mortar vendors.