amset will only work on the VIA connectors as the driver file does not contain any Promise support.
amset is VERY important. My new 536DX got from 20ms to 15ms by disabling the accoustic management (and it's still silent). While your 40+ won't be benefited as much, it's still a must!
Make sure your drive is listed at maxtor's site or is newer than the ones that are listed. (will check now for you).