Are you leaning one way or another? I honestly don't think that you could go wrong either way.
Cylinder versus box is a personal decision, IMO. After months of thought, I went with the cylinder. The two have been discussed here a decent amount, and SVS has a good comparison of the two
here.
Two versus one...tough choice. Some people here swear by multiple subwoofers. If it was me, I'd go for one of the new ones. But, I like getting the latest and greatest, and I also don't have room for two right now.