Ur-Priest, unfortunately, is the worst option as it doesn't really steal spell-likes, it copies them (despite the ability name). The memory-stealing spells are all Sorc/Wiz, whicch is outside the scope of Ur-Priest.
Didn't think of the last option, though. Doesn't look too bad, I guess, although it will require more to actually steal memories, it does get the ability to steal Su abilities.
In gestalt this would be super easy.