I have paddled the Tempest 170. It is a nice boat. I know of at least three people in our paddling group that paddle 165 as well. They all have the rotomold and love them. One of our group has even launched his out of a cypress tree(about 6 ft up) into a lake and will slide off docks and down steep banks into the water with his. He can roll it easily as well. The boat seems to take his antics well.
Don't know anything about the Valley Aquanaut....if you get a chance to paddle both, that may help you decide.
Not to muddy the water but,I personally prefer the Current Designs Cypress over the Tempest and there are previous posts to explain what I like about the Cypress.
Looking forward to see what other responses you have. Good Luck on your decision.