[rodneym]

Large Arbor,
I don't think you'll notice any difference with only 200 more cfm. It took me an extra 1000 to notice a few degrees.
I assume you're talking about the 16" fans. There's different profiles. The more room you have to work with, the more power you can get. It'll take a bit of researching the Spal website to figure it all out. If I remember correctly, the straight blades do more work (in a like motor) than curved blades, but the curved are quieter (no problem there!).
I think the only curved fan than sucks more air than straight might be a curved "paddle" fan, and that one (I think) is a higher profile. That was not an option for my setup but I'm sure you have more room.
Make sure you're comparing like fans to decipher which is "best" and of course what you can fit. I use the H.O. 16" fan which doesn't have a warranty. It's low profile but moves ALOT of air for it's size. The lack of warranty was a bummer but I still trust a non-warranted Spal over any other.