hate to be “that guy”
who's always trumpetting his own boat. But, I guess I'm the only one on pnet who has an Esquif Avalon. I think the Avalon fits the bill as a "fast" Royalex canoe. Actually its Royalite. Anyway, its theoretically a flat water canoe, but coming from Esquif, definitely has some whitewater capability in its DNA. It has 2 inches of rocker and a couple more inches of freeboard than other canoes in its class. I find it very maneuverable, although I have not paddled it in whitewater yet. I don't think its really intended for Cl III whitewater. But with a sprayskirt and some skills and lining/portaging the REALLY rough parts, it *might* work. It is a 16 footer, and it looks like you're looking for a 17 footer, so it might not be what you're after. But I thought I'd chime in anyway.
Esquif does have some 17 foot tripping models - a Prospector and the Canyon. The Canyon is highly rated as a whitewater tripper, but might not have the flat water speed you're looking for. Another option might be the 20 foot Miramichi, which I think gains some flat water speed due to its length. OT Tripper XL should be about the same, I would think.
The other big river tripper that comes to mind is the Mad River Expedition, which I think is the same as the *Dagger* Expedition co-designed by Cliff Jacobsen to combine whitewater capability and respectable flat water speed.