C2 is the next generation of Mervin BTX. It is Banana (Reverse Camber) between the feet and regular camber outside of the feet. It can be found on the Dark Series, which is one of the boards I am considering, as well as the Travis Rice blunt tip and pointy tip BTX's, Gnu Danny Kaas BTX, and Gnu Billy Goat BTX.
However, some believe that they stole this concept of combining regular and reverse camber from Never Summer.
steal or not, Never Summer did do it first, and C2 is the same as NS RC. But, its not like all these companies didn't follow Mervin's lead when they brought back reverse camber. Its all semantics, but ya gotta give credit where credit is due.
While MTX/BTX and NS Vario are physically different, they accomplish the same thing and ride quite similarly.
I havent been on the Altered Genetics line, so I can't speak to those. But I do know that either the NS SL or the TRS BTX will suit your needs. There tends to be not too much difference between comparable models of Libs and Gnu's just because they're from the same company.