I would buy almost any thermogenic product before Shred Matrix. After all of the crap Musclepharm pulled with mislabeling products, and the scams and crap with the Arnold Series, I stay away from the company all together. You'd be much better off with Hydroxyelite. Keep in mind it is a very high stim product though, so you might get jittery and have some side effects. Its a powerful forumula, but very effective.
Have you considered any other fat burners? Or were you between just those two?