Yes, but not just muscle cars...
TR6's are way down in price, as are C4 and C5 vettes, certain Alfa's, late model Honda S2000's, and more importantly from an investment standpoint, 230-280 pagoda SLs. If I were looking for an automotive blue chip right now, I would go with a pagoda. The crash that just happened in the last several years with Hemi values has saddled collector muscle Mopars with a stigma from which they may take a very long while to recover. Pagoda's by comparison, have a strong foreign as well as domestic following, so a flat US demand will not have nearly as severe a consequence for their overall market prices. On a fun per dollar basis though, I'd still take an X over all of them.
-Doug