Convert Cherokee 140 to 180?

Our 140 is coming up on 1600 hrs TBO.

We really hate what a dog it is and would like more power.

Planning ahead, we've thought of a few options:

1 - 160 hp conversion (this is almost the minimum we'd do)
2 - Powerflow exhaust (article in Plane and Pilot claims 20% power
improvement - can it be combined with #1?)
3 - 180 hp conversion

Anybody know about praciticalities, costs of #3 above? I know it would
require extra $$ for dissimilar engine exchange, STC costs, and
cowling/engine mount mods.

I know that some may say sell the plane and buy a 180, but we have a plane
whose condition we know, it has a pretty fresh paint job, it has all ADs
complied with, and we just spent ~$7K for a panel mount GPS. We have better
avionics than most and would hate to do the new buy thing and then spend a
lot extra getting the plane's condition up to that of our current one.