Lowest Cost GPS IFR system?

I have the GX55 in my Bonanza. They are approx $2K plus install. You
can install it either VFR only or IFR terminal/enroute. To be legal to
accept a direct clearance you will have to get it legal for
terminal/enroute. The GPS can be finnicky and it might cost hardly
anything up to a couple thousand to get it IFR legal. There are some
tests that the shop will run to make it legal, call any avionics shop
and they will tell you what is involved.

tom pettit tompetatpeak wrote:
I'm currently flying VFR in a vfr equipped plane. What would be the lowest
cost GPS based instrument system I could install and be legal for IFR
flying?

I looked through the last six months of this newsgroup, but didn't see a FAQ
or the answer to the above, so I hope it won't be something that was just
hashed out.

thanks,
tom pettit