erm, do you mean whats the power output from the factory head unit???? (Its pile of rubiish!!!) Or do you mean whats the most powerful headunit you can upgrade to??? Mine kicks out 4x50w (i think). Im not entirely sure what you mean, but i can definately recommend upgrading the standard stereo (factory speakers arent too bad, but they could do with changing to a named brand like pinoeer on something)
Hope this helps