Suttlaw, You asked about power cords with the SDS. I can recommend the Silent Source power cords for both the SDS and the motor. If you do put Silent Source PC's in the mix of cords you audition, let us know what happens.
As for cartridges, if you are first going to try a Benz---as some posters have recommended, give the "LP" or "Ebony" a shot.
SME IV or V 'arms on the HRX: Since SME 'arms require such a large cut away to accommodate the over-hang, sliding assembly (not to mention their low-slung DIN connectors), I would think that making such a large cutaway would make any other 'arm un-mountable after a SME has occupied the space. (The mounting holes are made directly into the base/plinth, right?) Also, the large cut-away for a SME would somewhat undermine the presumed design benefits of the massive, rigid, contiguous plinth/base of the HRX in the first place.
JMW 'arm connectors: I think you can get a VPI Phono Interface Box with a DIN connector.