Myself as well I would like one that fits inside the factory housing though, I don't want one that has a huge bulk on the back that's really ugly. I bought a 3200mah battery for my s3 & loved it as it kept my phone going hours more than the stock battery, it fit without adding a huge case to it as well.
I'm probably going with the Laza or Anker 5200mAh battery along with the Laza RuggedFusion case. Also thinking of trying the Zerolemon ZeroShock case with one of the 7500mAh batteries but that's probably just too big.