Most users start off with the Special Edition because it includes
a full orchestra with the most widely used playing techniques :
http://vsl.co.at/en/211/261/314/1605/1277.htm
Here are its content:
http://vsl.co.at/en/211/261/314/1605/1613/409.htm
Here are the computer requirements:
http://vsl.co.at/en/211/261/314/1605/1612/370.htm
If you are feel you need more then you can purchase the add-on
Extended library.
If you then need more articulations you can then move up to the
Special Edition Plus product line:
http://vsl.co.at/en/211/261/314/1606/1278.htm
At that point if you need more instruments or articulations
you can buy the "full" or bigger libraries that the Special Editions
originate from.
Its generally recommend that you use a PC or Mac that is as
powerful as you can afford to buy, with a separate hard drive
for the samples, and tons of RAM. Preferably a 64-bit system.
Hope that all helps.
DM33