I'm buying a fill neck for my new radiator setup in my K20A CRX. I will also need to buy a new cap to fit it. I was wondering what is optimal? I searched and there are about 20 threads with no answers. The mugen, and spoon caps convert over to about 18-20 PSI. They have units available at:

14-18 lbs.
19-21 lbs.
23-25 lbs.
27-29 lbs.

Just wonderin what you guys suggest. I'm going to buy the new setup tomorrow, and I want to make the right choice. The reason I am pondering this, is my old setup was using a standard GM cap(unknown psi), and my cooling fan was on allot durring stop and go traffic.