If you can afford it, the Leica survives for a reason. Small, very quiet, fantastic range/viewfinder and takes really fast lenses. A used 50mm f1.4 can run about $600 and an M4 about $600/700. For real fun, a used 50mm f1 Noctilux or 75mm f1.4 both sell for about $1,500 used.
Try one used at a local camera dealer. Once you use the Leica, anything else will disapoint.