Don't go overboard with reducing the amount of spells known. Psions get 36 powers known total and sometimes I think it's too small.
Well, unless you allow Pathfinder's favorite class bonus, human wizard/sorcerer style (additional spells known per level). Actually pretty nice choice instead of taking a prestige class. For example, instead of going Sangehirn with its Heal 9 requirement you learn Channel Power and research some healing.