Lees is a solid CB and Pearce is decent for low/mid premiership, Peltier wont cut it at that level but dont bother signing anyone unless its someone young who will develop, Your best bet is to just bring someone in on loan, Baker from Aston Villa is solid and can cover at LB too (Better defensively than Drury and White), You also have Austin who can drop in at CB and does a solid job there any money you have would be better invested in midfield, Apart from Austin Leeds are lacking all across midfield, Diouf is the only quality Leeds have in midfield apart from Austin but Diouf will unsettle morale he doesnt react well to any teamtalks regardless of the result he is just a nightmare to handle and will demand stupid wages to stay at the club after January.
I managed to win the championship with only 1 defeat with, Kenny, Byram, Lees, Pearce, Baker (Loan from Villa), Bebe (signed for 5k), Austin, Norris/Green, White, Becchio, McCormack/Ranger (loan from Newcastle), Also finished 8th in the premiership the following season with the same keeper/defenders and Austin, Replaced my midfield and attack but the defence is actually the stong point for Leeds.