I haven't really benchmarked a 32X, 36 or 40X CROMs but based on actual usage I don't feel that theres a difference in speed. So when I bought mine - an ASUS 40X - my decision to buy was not actually based on the speed but rather on the ability of the drive to read CDs. Sure, there drives that cost much less and are advertised as 40X or so but have you tried running one of your older games, or an archive of your fav utilities - with a little scratch on the surface. I use mine from running games to installing software and even watch VCDs, I've also gone into duplication of old database CDs that normally cannot be read by my previous drives.
I'm not really familiar with the Actimax but I've tried the Panasonic and I'd say it's a good choice too, if you can't get the ASUS.