$23k ?? How come?
Any of the CFIT accidents that I am aware of would most likely have been prevented by the use of a Garmin 296 with the terrain warning turned on. So OK, its not TSO'd and therefore you can't rely on it in an IFR situation.
A TSO146a Garmin 530W will do the trick - and does not cost $23k. The 430W will also do it, but it does not have the aural warning that the 530 does, so 530W or better is probably the go.
I have flown around a lot with terrain warning in the G430 in the Bo. If you pay attention to the warnings you are unlikely to be a victim of GFIT.
You can fly down the Hinchinbrook Channel at 500' paying attention to the terrain warning on the G430/530 and you will not hit anything!
...... but a Garmin 296 could have prevented the Lockhart R prang!
Dr 
PS: Hang on a minute ....... if the plan for ADSB had gone ahead, all or most of the aircraft affected by this proposal would have got heavily subsidised G530W, which includes terrain warning, anyway! Now who was responsible for scuttling that proposal?