They're looking at the NASDAQ and NYSE, They're not sure which one they're going to choose. Pyatt says he'll make his choice in the second qtr. and then get the paperwork going and they will be listed by the start of the third qtr. As far as obstacles, the should have no problem meeting all the requirements.
According to Forbes, they have already applied for listing on the Nasdaq...
From the article entitled "Billionaire Pharmaceutical Entrepreneur Makes Bet On Fast Growing Supplement Manufacturer: MusclePharm" (1/29/2013)
"Finally after an earlier reverse split, the company is eligible for and has applied to be listed on the NASDAQ exchange. The company believes, and I think rightly, that an approved NASDAQ listing will give them more exposure to institutions both as potential buyers of MusclePharm stock and for research coverage."