Since you are already familiar with the 4/3 format, may I suggest you very seriously look at the Nikon 1 line, particularly the V1. It will give you a really great little camera that will more than match the E-5 and with the LT-1 lens mount adapter, you can pick up some older Nikkor lenses and use them. The two lens system that is available with the camera will give you a reach of 27mm to 300mm, and by adding in a longer Nikkor lens, you can move that way down the field.
Unless you regularly print to sizes larger than 24x30, you will be very pleased with the output. Above 24x30, you had better be on a tripod if you want a sharp photo. A local car club just ordered one of the shots that I had taken at the Concours d'Elegance last November, and I sent it to a lab that I use regularly for large prints. They have it mounted on the wall of their club room. 96" x 120". I must say that I am very pleased with the way the photo looks. Here it is in low resolution:
