I've owned several Iwaki's, a Gen-X, 5 Sequence pumps, as well as some other odds and ends. I like the sequence hands down for servicability, support, quietness, and efficiency. They won't be more efficient than a http://www.aquariumspecialty.com/catalog/index.php?cPath=29_137_356">Red Dragon</a>, but IMO, they're some of the best you can get.
Like Sammy, I haven't actually used a Tarpon, but I've had very good luck with their entire range of pumps, and since they share parts across pumps, I would expect the quality to be just as good.
I do have three SEQ3200's that I use for various things, including a return from my basement- you might want to consider that model over the Tarpon...
Actually, weren't you interested in coming to see my setup anyway? PM me...