Here, i fixed your selection:
'09 335i - handling and speed
'08 550 - power & luxury
'08 C350 (yes, not a 300) luxury
Just get a PPI done at a reputable Indy shop, you dont need a CPO since it will just increase the price by $3000. I'm on my 4th BMW and none have been CPO, but I did take them for a PPI prior to purchase. A warranty is recommended if you cannot due the repairs yourself. GL.