I'm in the market for a AR to fill a similar role.
My budget is a little less than yours, but if I had $1600 to spare, I wouldn't even buy a production SPR. If you aren't able to do assemble it yourself, get quality parts from reputable manufacturers and let some one else put it together.
The areas on which I would concentrate are barrels, BCG, and trigger. It goes without saying that you'll need to free float the barrel. Grips, stocks, and stuff that is hung from the rail are subjective so no need to go into that.
For my budget and needs, I'm building on a RRA 2-stage LPK, Sabre Defense 1/7 20" barrel mated to a LMT upper receiver, and a BCM bolt carrier group. No glass, FH, or bipod -- I prefer the A3 removable handle, a good sling, and a compensator for this rifle.
If I had the money and the time, perhaps the barrel would be semi-custom, and I'd love to drop a Timney in there, but the SDI barrel is more than capable of performing in the role I have in mind for this rifle, and the RRA 2-stage will do for now too. It isn't meant to be a bench rest stick or anything.
Which ever way you go -- good luck with your search. BTW, that 6601 Colt is a good way to go to build up a decent DMR.