The SP's are the top of the line model at Pentax. Last year at SHOT I spoke with the rep at their binocular counter. Inside the Las Vegas Convention Center, there is a limit to how well you can test Leica, Steiner, Zeiss, Swarovski, etc.
In the end, I felt that spending more money on then what the Pentax SP's cost (respectively for each model), you were buy a lot of name recognition and generally very small improvements in performance for the cost. Don't get me wrong though, at the same price in the same performance class, I would probably opt for one of the big name German/Austrian/European makers.
My advice to you is to buy the best binoculars you can afford. If you only own poor to average quality binoculars, you will never miss the performance you didn't have. In my case, I have purchased and received many binoculars over the years. They generally failed with normal use. Had I bought better binoculars, I woudl have spent the same of less over time and, I would have had the joy of using better glass and the optical clarity it brings.