Perhaps a sparrow hawk overhaul could take me close to my 150/150 desires.
Speaking from first hand experience since I own both (see below, 150/150 on the left and 152 sparrowhawk on the right), the sparrowhawk STC does up the ante and makes the 152 a better plane with more giddy-up.
The 150/150 ups the ante even further and anyone here who owns one will confirm that.
By far the most important piece of the puzzle is finding a 150 or 152 without corrosion issues. We can fix engines, avionics and everything else but bad corrosion is deal breaker, period.
Good luck with whichever direction you take, Mike.