i have cubase le and sx3...
as stated before it depends on what u trying to do... LE is dated material based off of the SX1 edition
Cubase is currently at "Cubase 4"
therefore your Audio card could not be getting the current updates you might need. However, since it is dated software there's more support as in old message board posts and etc available on the net...
what type of audio interface card are you trying to get... because you tend to want a something that will grow with you.
i.e. upgrading to better equiptment pc or mac
new software windows vista or mac leopard
Just my two cents... and a couple of things to think about