Compaq EVO D300 Mobo Upgrade

We have a number of Compaq EVO D300 convertible minitowers (circa 2000, with 1.5Ghz P4) with 250w power supplies, which we’d like to upgrade. Due to some interesting asset policies at this company, we can’t simply retire these units and go with newer models, however we can upgrade the insides as much as we’d like. Unfortunately, upgrading the low wattage power supplies isn’t possible, as they are an odd form factor, so we're stuck with the cases and the 250w power supplies. Everything else inside is fair game.

Are there good mobo’s out there that can operate OK on these low wattage power supplies, and still provide a decent level of performance?

The existing Compaq mobo looks to be similar to a Micro-ATX form factor, I think, as they’re nearly square at 243mm x 248mm (about 9.6” x 9.8”). I believe the cases will accommodate a full ATX mobo as well.

Thanks very much in advance for your recommendations.

Check out the cheaper MSI motherboards which only hold 4 gigs of memory max with the 2 memory slots for a start.