JHaines...
With all do respect to those with BUIS on their M4gery's, Carbines, and SBRs it wouldn't really benefit you to have these sights on the weapon. Aside from defensive SHTF situations, you'll likely never "lose the scope" and hopefully with that Varminter set-up you'll be shooting at such distances that the BUIS wouldn't likely getcha on paper. I'm working on that same set-up right now, and for what its worth I do not plan to use BUIS. However, I read a thread here once that stated the front sight base (plain not folding) would not interfere with the sight plain. Something about the optical plane or ellipse.....something sexy like that, anyways I threw my scope on one of my other ARs' and sure enough you can see just fine right "through" the FSB. Good luck on your build.
Also......the dissipator if I'm not mistaken costs much less than the Varminter, but I'd still go with the Varminter.