Those sound like good challanges, Geno and Cory's tunes...

I just found one of the nicest songs I ever heard on Cajun Accordion, played by Cory and his band... website link 1

ha ha, i thought it sounded familiar
makes a pretty good two step though
wle

Another excellent tune to learn is the "Domino Two Step" by Nathan Abshire. This tune will build speed and dexterity in your fingers. I purchased it from iTunes and learned it with the Amazing Slowdowner. It took a while but it was well worth the effort.