Yep, the object of the "block bowing" is to point load the center of the IHS area and get much more contact pressure at the source of the heat (the cpu slug underneath the IHS). Also, the base thickness of today's waterblocks is pretty darn thin, so you get some minor non-permanent deformation when clamping pressure is applied, which makes the actual contact area larger when properly mounted. If the thin base was flat to start with, there is the possibility of actually deforming the base under pressure enough to remove contact pressure at the center of the waterblock base, since the clamping pressure is applied around the outside circumference of the waterblock.
In other words, do not lap the base of your new waterblock. These blocks were designed and extensively tested with the bow in the blocks, which has been found to give best performance. This ain't 2001 and these waterblocks aren't old DD Maze 1 or Maze 2 designs with 1/8 to 1/4 inch of solid copper meat between the base and water channels. If you want to lap your processor, then knock yourself out. But in most cases, you won't see significant performance improvement after lapping the IHS either.
EDIT: Forgot about the original question. If you go dual fan rad, I would suggest that you go with a rad such as a PA120.2, GTX240, Feser 240 or RX240, which are on the higher end of the double fan performance range.
