[Gooserider]

You are right about less resistance from parallel rads, assuming that the extra plumbing needed to put them together doesn't cancel out the lower resistance.

On the second point, more rad surface is not necessarily a good thing if it causes lower air flows. Thus far the designs I've seen suggested in this thread would have far less total airflow than a single rad design, which will cause WORSE cooling, not better.

Growth is not that big of a problem, assuming you start with a reasonable size rad. The proposed designs featured a 6" x 9" x 2" rad, which is more than sufficient to cool any single PC. This is especially true if using a single pass design core like the FedCo # 2-342, which is about that size. Assuming an actual flow rate = to 50% of the free air rating, and a 10*C MAXIMUM temp increase, then the 2-342 will handle approx a 500W load w/ only two 120mm x 32mm fans with an 80 CFM rating. (and this is a very conservative estimate) By my estimates this would be enough to cover a system with dual CPU's, a hot video card, and a good assortment of NB's, HDD's, etc. plus a high power pump, with plenty of margin.

Remember also that approaching ambient is an asymptotic curve, so doubling the rad area is NOT going to halve your Delta T. Depending on how close you would have been with a single rad setup, doubling the area might only get you a couple of *C, which is hardly worth it.

Gooserider