well its got a serial doo hicky attached on it, not that its really that hard to control a hbridge and the op already has it and paid for it ...
otherwise I would use the L289 in the though hole package and screw a heat sink to it, but that adds weight and maybe balance problems for a remote rover platform
I dunno, it may not be that big of an issue after startup to even go that far, its just getting that inital kick that seems to be the issue