Wheels, then pedals, followed by bars.
But, really, it's all down to riding style. You can buy nuke-proof BMX platform peds, and need never worry again, and Nitto and Velo Orange bars can usually take more than even the clydsiest of clydes can dish out.
Wheels, tho, they go out of true even if you look at them hard. The mantra for the clyde should be "Shift early, shift often, mash never!"
Yes, once we tons-o-funs get up off the saddle to stand on the pedals, we can beat Lance Armstrong and more than a few Top Fuel Funnycar drag-racers in the 0-25mph bracket, but the cost will be pringled rear wheels, busted chains, munged cogs and bent pedals.
Shift like you mean it, stay on the seat and steer clear of pot-holes and curbs, and your wheels will love you back.