Dear Rifo,
As far as I know ISE webpack allows programming Spartan6 devices up to LX75.
It has always been like this that webpack only allows small FPGAs. After all the LX100 is a huge device.
You can also use 30days trial version (all features).
If you come from university then the license is not very expensive.
Every company is trying to earn some money.
Sorry,
Ales