If you are considering keeping this optic for a long time then you want something pretty top end with a really good warranty. Trijicon and Aimpoint are both really good options here.

The RMR is light, "just works" and can take a beating.

T1's and T2's (2moa) are very fine, precision optics. Both are really good at what they do, both are super tough as well.

I would wait until the MCO comes out and people get time on guns with it, especially before you make any decisions.

I ran the piss out of an H1 (4moa) - http://www.vdmsr.com/2012/12/aimpoin...larue-751.html - and it worked really well, you could probably get one fairly cheap, used, if you wanted to.

I would consider a pairing with a magnifier (I'd had great success with the 3.5x from SamsonMFG, but there are others that are really good).

Bobro for mounts - they are simply the best, period, and they warranty everything.

How quickly do you need it?

I just finished a review of the Vortex Sparc II (http://www.vdmsr.com/2015/08/vortex-...-sparc-ii.html) and if you want to give that a try to see what a good RDS with a bunch of features feels like, I'll send it to you, no charge, return when you're done with it.

edit; just to add - Maybe a quality 1-4x is what you really want for a 100y gun. Obviously there are tons of these out there, but they hold their value on the resale market (buy used, sell used) and you could jump around with features - would be total cost of RDS + magnifier + mounts = quality 1-4x with a mount. Again, Trijicon makes a great optic that works well (Accupower) and you don't need a magnifier.