Can anyone recommend a suitable component speaker to upgrade the factory fronts on an STi? (ideally without having to change the mounts)

I have a Sony XM404 Xplod amp (40W RMS into 4 channels) and I'm looking to fit that using the factory CD/MD head unit (jap spec.) and the existing rear speakers, upgrading the fronts.

Any suggestions as to the best sounding brands and/or info on what size speaker will fit the front door mounts?

Thanks for any info!