I was seriously thinking about getting this done to an EK9. I had a passenger ride in a K20 EG and it felt really fast, but then I had my dad drive my own B16b EK9 on the same roads about 10 minutes later to compare and, though there was a noticeable difference from around 3rd gear upwards, I decided it wasn't enough to warrant the money at the time.
I'm waiting to see how Haitch on this forum rates the K-swap for trackday use and then go from there. I've seen EG K20's going for £6,000'ish pounds which is very little money considering the work and cost of parts, but I don't see them come up for sale often.