FWIW, I'd probably skip on panniers with the RX's.
1) They are really designed for their own bags with the side bags (e.g. the RX Trunkbag EX)
2) Weight capacity is pretty low, 15-20 lbs depending on the model.
3) You can't use both a pannier and the Topeak bags that slide into the rack (the RX types)
If you're going to use panniers, you might as well use a real rack. If your bike doesn't have eyelets, you can always use P-clamps or, worst case scenario, use a rack that clamps onto the brake bosses.