Parts in total came to a bit under $2000 - that's another head, new cams, new cam gears, new technotoytuning adaptor, new gasket, new springs, quads, trumpets. Then I have to add labour for porting, to fit it (not so straight forward in my car - AH Sprite) and reprogramme the ECU. I reckon I probably saved around $800-$1000 on parts by scrounging around a bit. I didn't need to buy a new ECU as I have the Motec. Might get a few $ back from my old head – complete & with intake & TB & TPS (complete - anyone want one?). I'm sure I'll be spending some considerable $ to port the head, set it up and tune it on the dyno. I am not touching the bottom end at all.
It could be a WHOLE lot cheaper by forgetting about the quads and putting in slightly milder cams that work with the stock ECU.
The decision to stick with the 16v was pretty much made for me because it is already in and there'd be heaps of work to get something else in. If I could easily swap it, I would have seriously thought about a 4agze or turbo. Not so sure about the 20v.