If you already have an amp you might want to check out amp modelers. These beasts either plug into to the front of your amp or directly into a desk. Lots of people make them however some are better than others. Im using a Line 6 POD and it is fantastic, however I started with a Boss GP20 amp factory which really really sucked ! I have a Digitech GNX2 in the post at the moment (It is getting delivered on Monday and Im hopping up and down with excitement) so stay tuned for more of my humble opinions !!!!

Cheers
S