Engine confusion, would like your thoughts!

[DC2-PWR]

Define properly?

Fitting engine
New Mounts
Re-wiring
Changing most of the front bits (so things dont break)
Bigger brakes (more power, but still stock parts)
etc etc etc

And so it counts on. So when I read that people say its "cheap" to upgrade to a K20 just like that... hard to believe

I'd say go B20, lots of potential. My mate had a B20 DC2, fark that thing went, ripped up any B18CR eg with i/h/e hondata, 180sx type x etc
+
Most of your stock parts are capable of the engine, so cheaper in the long run meaning more fun in the short run.

If you had a good 10-15k for the K-series then go for it.
Or
For a long term project for the k-series is another good idea, but then you need another daily to get you around