Austierro Neangelion
Even though I don't train in the art itself but to improve on your power in striking, try doing those wrist exercises with the pull down weight machines, that can increase the power in the force of your strike and work on your tricep, maybe close grip bench pressing or high elevated bench press can help...I dunno...
razz
for wrist strenght i would recomend exercises like the upright row or even bicep curls that put a strain on you wrist. also you may have seen a small bar with a weight attached to it on a cable at you local gym (for some reason my brain is drawing a complete blank on its name) the idea is to roll this up then down again with your arms fully outstreched (great wrist exercise). avoid machenes if you can as they don't do much for your joints.
also one of the most effective way of strenghting your wrists is simply to strech regularly, as this increases blood flow which in turn strenghtens the joint.
most important muscels for boxing are the deltoids so work all 3 hard with free weights.
hope this helps.