The PowerXL drive will have to do the same as the Chinon FB357A in an A4000 - it needs to run at 150rpm. How it does this I'm not sure - you may well find that the drive isn't an entirely normal PC drive, and is dual-speed like the afore-mentioned Chinon. That said, the controller chips must do something funky, and the HighDensityPatch is obviously necessary for something....
Basically be aware that the apparently normal drive in the XL drive may not be as normal as it seems!