no no your all wrong... you could go titanium light as a feather and stronger than anything you currently have. GT have a Cradlemount titanium frame but never really got sold much due to the pricetag of 2k for frame alone. stunt101 is right though, chromo is the way, seems to be the strongest material for weight ratio.
there is nothing bad about the steel frame as long as its constructed well with good weld joins plus the needed extra bracing here and there. good suspension is the key.