Hello Capnmtway and welcome aboard!
If you're going to spend the extra money on an aluminium trailer, then IMO the Trailex SUT-350-S is the best way to go. They've designed a great trailer for these boats and they're a great company to deal with. Some people find that using just 2, TI saddles is adequate, and others like having 3. I used 3 saddles for two basic reasons; support, and ease in launching and retrieving. viewtopic.php?f=69&t=35469
Tom and Stringy are correct, you'll need to order two sets. However having a spare may come in handy down the road. As Tom mentions, a stern roller is mighty helpful and a bow stop too.
Contacting Trailex directly is the best way to get a current price on the Crossbars. I bought my over three years ago but they weren't that much back then. As far as bolting the saddles to the crossbars, you may need to drill the holes slightly larger inside the saddle wells to accommodate the Trailex T-Bolts, I know I did. I also drilled a drain hole in the same area.
Have fun assembling it, take your time and then get out there and start enjoying your new boat
BTW, where are you located?