If you’re buying a hiking sac for cycling as well, be careful that it doesn’t sit so high that it fouls your helmet on steep descents when you’re having to tilt your head back to see where you’re going. Not funny, guess who once crashed into a tree thanks to that one…
It sounds like it’s out of your budget, but Osprey have just launched a bunch of bike-specific larger packs called Escapist, kind of like the Talon, but specifically for cyclists.
Alternatively, have a look at the lightweight packs aimed at mountain marathoners and adventure racers, which tend to sit lower and be designed for stability when running/bumping around. Stuff from OMM and innov-8, also Terra Nova, for example.
Wingnut, again out of your price range, I guess work really well.
Personally I wouldn’t want to even think about riding with a 40-50-litre pack, but each to their own. You can get away with relatively small packs, even for overnighters these days, walking that is, because modern lightweight kit is much lighter and smaller packing than it used to be, but – a bit like bike stuff – its also very expensive once you start shopping for the top-end stuff.