I got set up with a CZ 457 synthetic with a 16" barrel and Athlon Argos BTR Gen 2 6-24x50 scope. I added an arca rail from amazon and made a custom cheek riser out of Kydex. It fits well and shoots well. I did see that Vortex just put out their 5-25x56 Vortex Venom with a 34 mm tube which is production legal. It looks like a nice scope that is an upgrade over the diamondback tactical and you get an extra 6 mils of adjustment in the elevation over the athlon.
I was also looking at the Tikka T1X but decided on the CZ.