After taking way too much time contemplating an $80 purchase, I finally broke down and bought a CCD scanner. The difference in scan quality is (as others have said) remarkable.
The OP was spot on about leaving the lid open, too. Despite giving a PSA holder an SGC-looking appearance, scanning this way does deliver great contrast.
Old scanner:
New CCD scanner:
Time to go re-scan my graded cards and (finally) have crisp images of them.
Have a great day, everyone.
Best Regards,
Eric