I get great dirty chime out of my JTM45. All I have to do is crank the master volume and I get into Dave Davies circa 'I Need You'. If that isn't great garage tone, I don't know what is.
I think more than the amp, it's important how to eq. Lots of treble w/ mild overdrive and fuzz to kick you for leads.
People also say don't use Gibsons for garage rock and again I'd say with the proper eq and playing technique you can get a great garagey tone. YMMV but I have to stand up for my own gear. :D