P3dV4 & P3dV4.1 are latest flight sim iterations. They are now 64 bit,and very stable. For the 737, you can't go past the PMDG 737NGX. It has an SDK which along with FSUIPC and suitable I/O boards allows one to have as many switches, rotaries, etc, as you like.
The P3D versions are either Academic or Professional, depending on your status. Some good control are from GoFlight,Virtual Fly, PFC, but they are expensive.