From Native Instruments:
Guitar Rig is a complete solution for the modern guitarist - on stage, in the rehearsal space, at home, and in the studio. The software provides authentic emulations of classic and modern amplifiers, cabinets, microphones, and effects, letting guitarists easily create any guitar set-up imaginable. The outstanding sound quality, extensive features, and wide ranging flexibility set Guitar Rig apart. Guitar Rig 4 is available in various versions for different requirements, including the full-featured "Pro"software version; the "Kontrol" version that bundles a full-featured USB foot controller hardware with integrated audio interface; and the entry-level "Essential" software version that offers most of the features at half of the price. To achieve the best possible audio quality, the guitar must be connected to the computer through an audio interface equipped with a high impedance ( "Hi-Z") instrument input, or via a DI box or guitar preamp.