well technically caffeine restricts the blood vessels, while on the other hand, Nitric Oxide widens them..so i think it might possibly cancel out the effects...but as a part of BSN's Mass Stack, they recommend N.O. Xplode, Nitrix, and Cellmass. N.O Xplode also has caffeine in it, but it still seems to work fine with Nitrix. i guess they purposely make it so that their own products work perfectly when combined, but not so well with other products. so personally i would try stacking Lipo-6X with Niox as both are made by Nutrex and make up 2/3 their "cutting" stack, with the only other product being Vitrix. hope this helps any.
The iron never lies to you. The iron will always kick you the real deal. I have found the iron to be my greatest friend. It never freaks out on me, never runs. Friends may come and go, but 200lbs is always 200lbs.