Okay guys, I'm new to the AR game so I could use a little help. Also before anyone asks, yes, I tried the search function and I have absolutely NO luck with it on this forum for whatever reason, so here's my situation..
I just bought my first AR which I will pick up tomorrow. It's a RRA Elite mid-length with a 16" 1 in 8 twist stainless barrel and upgraded BCG, and Dominator II mount. I have a new Sightron SII 4.5-14x42 AO Illuminated Mil-Dot reticle scope that I want to put on it.

Now, I may at some time in the future decide to take the scope off for a while and play around with an Eotech, so that is why I ordered it with the Dominator II. What I do not know however, is what I really need to properly install the Sightron scope. The LaRue Tactical SPR/QD LT-104 Mount looks like it would work, but what the hell do I know??? Is something like that what I am going to need? If so, is LaRue the only game in town? I have nothing against LaRue, I would just like to know what my options are and if there is anything out there that is of equal or near equal quality for a little less money(better bang for the buck) than the LaRue.

I have poured over all the picture threads and what not guys, but I'm still a little lost on this one fellas. I sure wouls appreciate the help. Thanks!

There are a couple of options for mounting magnified optics on an AR flat top, and a lot depends on how far forward you need the scope mounted to get good eye relief with your preferred cheek weld.

- High or extra-high rings: can give enough height, but often don't have enough eye relief.  This is the least desirable option, IMO.

- Extended scout riser, with rails that extend over the handguard:  These typically add 1/2" height, and will work with medium or high rings.  This is the most flexible option, but there are more connections between your scope and rifle that can shift or loosen.  RRA, YHM, ARMS, and others make good ones.  I like this on guns that I switch optics around on a lot.

- One-piece scope mount, like the LaRue:  Solid, but not much flexibility.  These generally give a good height, but vary in how much eye relief you can get.  The LaRue's considered the best, and if you don't mind spending the money, it's hard to go wrong.  Next best option is the Armalite one-piece, which is half the price and is very solid and sturdy, but is only semi quick release, with thumbscrews that protrude a good bit.  After that, there's a bunch of others, but some of the cheaper ones don't give much more forward positioning than rings on the flat top.

For a full-size scope, I'd either go with the Armalite for under $100 or the LaRue for around $200, or with an extended rail and good rings.

That was a very helpful post maxicon, thank you very much. So, when I get ready to mount something like the LaRue or Armalite do I first remove the Dominator II, or does it stay?

You get rid of it.  You cant have a fixed rear iron with a magnified scope and the riser is the wrong height for the scope as well.  What you want is a Larue mount for the EOtech, a folding rear sight like the Troy and a Larue SPR scope mount of some flavor for your magnified optic.  The BUIS stays and the EOtech and scope can be swapped with no loss of zero at will after that.

Thanks Devl, that makes sense. Hopefully I can get something for the RRA Dominator II, if not I will start an AR parts box I guess. The more I look at the LaRue stuff, the nicer it looks. And they're Texas boys to boot!!!

Could he not use a scout rail with an Eotech? I use only irons and glass. Could you not remove the Eotech and put on an Armalite and scope combo? Not trying to hijack the thread, but I was just curious.

Would this not be the same height off the rail as a Dominator with an Eotech?
Sorry if this is a dumbass question.

What setup is that in the above pic?

Burris Fullfield Tactical 2-7x35. Armalite mount, YHM 5" scout rail, Matech buis. The only reason I added the scout rail was because the scope would not clear the buis. I like the buis so I had to add a little height. RRA Entry Tactical.

So, can I run a Troy BUIS with a Larue SPR scope mount and make it all work?