Own a POF Revolution DI, love it. The SF10 small frame is the same weight but with a 12" barrel instead of the Revolution's 16" (unless you're going for the pistol version?). To get lighter, you're spending $1200 more on the SF10 Nighthawk which has a lot of possible customization. Either version lists a lot of high quality components.
On the Nighthawk, not sure what the actual configuration is for the 5.8lb. version nor what the final price might be. Could come in substantially higher.
Then there's the consideration on what's actually available and how long you're willing to wait. I did look at the F4 Nighthawk but in the end it's price was a bit too dear at this stage in the game. You should also take a look at VSeven.