Check out this site, from Mud_Chan on gamefaqs:
http://sites.google.com/site/darksoulstats/dark-souls-calculators/catalyst-talisman
Can input your Int/Faith levels to see what the highest MagADJ catalyst would be for you. Because of this, Int or Faith builds are one of the only stats that it's worth pumping all the way to 50. For example, at 30 Faith, the best talisman is Canvas at 172 MagAdj At 40 Faith, it's still Canvas at 190 MagAdj. But then at 50 faith, Darkmoon Talisman takes over at 226 MagAdj, which actually is a bigger jump from 40 -> 50 faith then it was for 30 -> 40.
Also, according to his post on GameFAQs, the weapon enchants have different multipliers:
http://www.gamefaqs.com/boards/606312-dark-souls/60801727
Darkmoon Blade has the best multiplier at 1.8x your MagAdj (and can be upgraded even further to 2.1x if you grind rank in the covenant), while Crystal Magic Weapon tops out at 1.4x. However, that doesn't take into account Tin Crystallization Catalyst, which has no equivalent talisman, and has 293 MagAdj at 50 Int.
Also, your idea for a Dex/Int or Dex/Faith build makes me wonder if you can build an SL120 one-hit KO backstab build using a dagger/rapier and enchanting it with CMW/Darkmoon Blade