I have Capuano and Madlung as my two primary CB's Madlung still going awesomely strong even in 16-17 season. My two CM's are McEachren and Thomas Carroll both transfer listed both the pair for under 2 million.
CB - Morrison from Charlton, quality CB.
CM - Stuart Armstrong is good for the league, you have a beast in Biton and have plenty of CM's unless you sold Ledley, Kayal, Brown, Rogic, McGeouch and Mulgrew can cover there too.