I really don't think trad DSLRs are the sensible budget option. Long lenses for full frame are big, heavy and expensive, and none of the big mfrs dared queering their pitch by introducing long lenses for the smaller DX sensors. So you pay for FX lenses you don't need.
The lenses available for m4/3rds are staggering in comparison - small, fast and way cheaper for the same mag. The Olympus 40-150/2.8 pro and dedicated 1.4x is the chief appeal of m4/3rds for me, ~£750 used. AF won't be spectacular on a cheap old body but unlikely to be any worse than a D300/7D moving budget full-frame glass about.