I've found that Silix is usually hard to beat for price. Ruby is the only dealer that comes close. With the SMP, wherever you go, you're probably going to get the same exact watch, so just look to make sure you get the best price. Silix sometimes will cut the price a little on some of his older models, and he may give you a slight discount on the SMP.
The PO is a different story. If you're looking for the 42.5mm, Silix's watch is the same as the other dealers, and much cheaper ($150 with ETA). Silix's new 45mm, however, is different than Josh's and Andrew's Ultimate. You'll need to make the decision as to whether the differences between Silix's 45mm and the Ultimate are worth the price difference.
Other thing you may want to look at is Josh's and Andrew's so-called Ultimate Lite. Basically the same as the Ultimate, but with an Asian movement instead of an ETA. It's a lot cheaper, and it's gotten some very good reviews.