Best mp4 settings in Compressor

Hello! I'm sure this question has come up numerous times but I've spent the past half hour searching through a the forums and have only found a few bits of information.

Bottom line - my mp4 encodes out of Compressor look terrible. I've tried almost a dozen different settings tweaks and still can't seem to find anything good enough. My main goals are to achieve a web playable file at 640x360 using a .mp4 extension, H264 compression, and an average bit rate around 750. My original file format is ProRes 422 1920x1080 60i. OS is 10.6.3. Compressor version is 3.5.2. And I'm encoding on a Mac Pro 2 x 3Ghz Dual-Core Intel Xeon with 10Gb RAM.

I have to output 3 different formats for a client for every project we do - which is multiple a week. The DVD and .mov files I'm sending out look fine. But I'm having to separately take each file and run it through another software package to get a clean MP4. It would REALLY help my workflow if I could come up with an mp4 encode setting directly in Compressor that would let me batch everything at one time.

Thanks for any suggestions.

Don Hertz
AC Media