IFR GPS

I seem to be having a hard time grasping this...

My ADF has taken a nose dive for the final time and I'd like to install an
IFR GPS to be able to use it in lieu of an ADF and DME and the moving map
would be nice as well. ( I fly with a handheld Garmin 196 already ). So
here's my problem. I think I'm about two years away from installing a whole
new avionics package with a MFD etc... So, I'd like to keep my costs down to
a reasonable level at present but still have a very workable system that
gives me the option of a /G flight plan. GPS approaches are not what I'm
really after here. I'm getting conflicting advice on whether I need a system
with the annunciator and an OBS for the GPS or can I have the 89B ( or
similar model ) installed and simply use the readout from the face for legal
IFR enroute flight? Or am I going about this all wrong to start with? Having
never flown an aircraft with an IFR approved GPS, I'm kinda confused about
what to do. The cost between the two setups is substantial.

--

Steve in Cleve