I have a TEAC CD-W540E drive. I got 50-40x TDK CD-R80 disks at CompUSA for $2.99US after $17US in rebates. Here are the results I got using CD Speed's overburning test.
At 40X --
Manufacturer: CMC Magnetics
Capacity: 79:59.74 (703MB-data) (807MB-audio)
Maximum: 82:29.24 (724MB)
http://www.buy.com has these disks for $7.99US after a $10US rebate. You can get up to 150 disk (3 packs of 50) and there's no shipping charges. Offer expires at the end of June.
Just relating to the drive, I burned 700MB of data/10 files, in 2 minutes and 58 seconds. 850MHz Athlon & IBM 120GXP drives using UDMA66. I will be getting some new hardware soon. I will report my findings again if there's a big change.