IK Multimedia just came out with this new package for computers and for Ipad and Iphone versions of Amplitube.
It includes 2 officially licensed Slash Marshall amps including the JCM Silver Jubilee and the higher gain AFD100, plus several new pedals that he also uses. Cabinets are the Marshall 1960AV.
For desktop computers, you can buy these individually in the Custom Shop, or get the whole package for $79.99 (cheaper than buying them all individually).
http://www.ikmultimedia.com/products/slashcs/
I'm looking forward to checking these out. I'm excited that they're working with Marshall now for officially licensed products and hoping they'll do more.