all speed is a dangerous claim, for ANY CD-R! since most CD-Rs don't burn very well at 1x or 2x anymore! not to mention whether the staement will remain true with new technologies and speeds coming out in the future (though this may no longer really be an issue).
I would recommend Maxell 40x CD-Rs, as they performed VERY well during my testing. Unless you can find out WHO makes these Harmony CD-Rs and make sure it's a manufacturer of good reputation, I wouldn't go for them. Find some good 48x compatible CD-Rs that you KNOW are good, and see if you can push them to 52x