Since you usually wear your PC is it safe to assume that the dress is dinner jacket for those not in kilts?

If that is the case then I would stick with the PC and white shirt, cream hose and white sporran your other choice doesn't sound quite right for black tie.. If the dress is semi-formal then give it a go. I think a semi-dress sporran would be a better choice than a formal one and i am not sure about the hose, I would probably need to see it. black hose might be a bit to much but who knows.