Not sure what you mean.
Like, a Psionic Cleric? A Psionic Ranger?
The Psion is already a psionic Wizard or Sorcerer, and can combine nicely with a Scout, Ranger, Rogue or Fighter (and prestige into Elocator or Slayer to keep up multiple roles).
The Psychic Warrior is already a psionic Fighter, and there are some nice variants which make him into a psionic Monk (basically, take away armor prof. and instead grant Wis to AC, monk AC bonus as he levels up, and Improved Unarmed Strike + Monk weapons instead of all Martial weapons).
There's a psi-flavored Warlock ("Psilock") which some nice folks around here helped design...
So, which specific PHB class are you looking to replace?
Cheers, -- N