Lots of info here
On the forum, there have been many discussions on this. If you do some searches in the forum archives, you will find tons of discussion on this.
THere are two large SW coolers with similar size and fit to the Niagra 2006A. They have two different internal routing paths, one is single-pass, the other is two-pass. the consensus seems to be that they are noticeably better.
The archives also have tons of discussion about the merits of firewall mounted vs. baffle-mounted coolers. Lots of good pictures of installations.
You will find that there are sort of two camps in the discussions. Those that have too much cooling and have some of their cooler blocked off much of the time, and those that have OK, or marginal, or inadequate cooling. Aside from the obvious reasons like leaky baffles, unknown leak paths in the upper cowl, etc, there is one common distinguishing factor. The angle-valve engines have piston-skirt oil squirters, which help cool the pistons. This generally leads to cooler cylinders, but hotter oil. So if you have an angle-valve engine (like me) then you will want as good a cooler as you can get.
I was marginally happy with my Niagra 2006A, and was considering switching to the SW 10599. Then, I decided as a last try to caulk the edges of the cooler where there was a series of very small leak paths where the cooling fin channels end. It made a noticeable difference - enough improvement that I am now very happy. You should be able to find that story in the archives too.
Hope that helps get you started.