Hi,
All of the above suggestions are sound, but why are you only seeking to max out these skills; why not try to go above par.
Consider dipping into Warlock for two levels.
Onlt 2+ skill points per level, but
The Invokations you would want are
Otherwordly Whispers +6 profane bonus on Knowledge(Arcane), Knowledge(Religeon) and Knowledge(the Planes) [CMage p 124]
Beguiling Influence +6 profane bonus on Bluff, Diplomacy and Intimidate [CArc]
Thus you are netting 20+ skill points per level and are setting 6 of your skills at max+6
What else do you get for your experience pieces ?
1d6 Eldritch Blast, which is pretty inconsequential except perhaps as a vehicle for an occasion magic ranged touch sneak attack.
Oh and you also get Det magic at will.
The cost: you have to be Chaotic or Evil.