If you can't succeed with Benzema then I don't see much hope for you with Aguero or Suarez. Your tactic sounds like it isn't necessarily suited to the PPMs offered. Suarez will hold the ball too long and Aguero will drop deep. If your midfield is conflicting with this then they won't perform. Benzema has moves into channels, places shots, plays one-twos and cuts inside. These are easily viewable in the information section as they are popular players. I'm guessing Benzema is too busy trying to receive a ball in an attacking-possession based team... but these are just assumptions. It's impossible to suggest if you think about it.
So go with a blank canvas for better results.
I suggest Batshuayi.
He might not perform amazingly but without looking at your entire squad one by one and without looking thoroughly for discrepancies in your tactic it's impossible for me to suggest you a player. Especially one as expensive as those guys as you will be gambling/guessing and most probably end up disappointed in your results/striker.
YMMV, IMHO, SMB, etc. :$