Here I used the GarageBand default Clean Combo. I recorded one chorded riff direct and then just went through all the amp models with the same recorded riff. You can easily hear the difference between the amp models.
The Mesa Boogie Model certainly is not clean at the default settings even though Apple labels that setting as Clean Combo. I guess this is characteristic of a Mesa, but I've never really played one so I don't know.
I have played either originals or versions of all the other amps and as I stated earlier in the article, they give you the basic flavor of the real deal.