Hi,
I own a T2 which is the same as the T3 but with 76 keys. I have ask my favorite music store for a EX-upgrade and they contacted KORG. Answer: the is no way for upgrading. But this was 3 years ago.
The EX-option is not so usefull as it seems because you can only load the samples from the disk. After power off all sample are lost!
If you find a way to read T3 disks with a PC, please let me now. I'm looking for this for years. Please send an email to kay.anbuhl@daimlerchrysler.com

KAY