
StreamOfTheSky |

There isn't any good way to enter early.
Even with the new ruling that spell-likes help you qualify, if you played a race w/ a level 2 spell-like ability, you'd still need +2d6 sneak attack. You could go [Sneak Attack class] 3 / [Arcane caster class] 1, but then you'd lose 3 whole caster levels!
You're much better off in the long run doing 1 level in a SA class, 4 levels in the caster class, then taking 1 level in Sleepless Detective (the better PrC) or Assassin. Unfortunately, both of those require 5 skill ranks, so you can't enter them any earlier than 6th HD.
If you don't care about losing a ton of caster levels, I guess using the SLA trick would get you into AT at 5th HD instead of the normal entry of 7th HD. I seriously don't think losing another CL is worth the early entry, though...