The end of the E-System as we know it!

[ianpinion]

Buying better lenses will only improve the clarity of your images because of the better optical performance of the lens, but you still need to know how to use it properly to gain it's full potential.

As for depth of field, well if you use a lens that will open up to a very wide aperture then you can still get a very shallow depth of field. My 12-60mm f/2.8 - f/4 is very capable of producing shallow depths of field.