I have been playing through an iRig HD2 the last couple of days using Amplitube. Very cool setup. I don't really know what real equipment I want so this is a good way to cheaply experiment.
Is there a simple setup for being able to hear the computer audio (YouTube) and the guitar at the same time tho? On iPad it seems like only one app can have the audio at a time, and on Windows, you get the same behavior using ASIO 4 All.