I’m tempted by the rear light from DX, looks a bit mental! And would free up a batery as a spare.
Other than that I go for the “more the merrier” approach.
If you buy the cheep cateye LED sets wehre the frotn and rear are identical in all but colour, then swap the lenses over you get a red LED in a clear case (Lexus style innit!) and a white LED in a Red case, turn them on and it all looks the same. One of those either side of the big reflector on the back of the pannier.
A blackburn Mars on my seatpost angled slightly up from horisontal.
And I usualy have some small white LED’s on my bags sternum strap to illuminate me a bit.