Vann's has had those Mirage speakers "over 50% off" for a while now (I want to say years), I don't know what to make of it, but it is what it is.
Onto the impressions:
The Nanosat speakers that you can find on Newegg and at stores like Best Buy seem to be yet another "Bose clone" attempt; something small and cute to meet WAF. They don't sound terrible, but they're not giant killers. They go over a cliff at some relatively high frequency, and that makes them very limited for real listening enjoyment (you *must* use a sub).
The nicer OMNI and OMD speakers are a bit more robust; the OMNI-550 and the OMD series can stand without a sub in many rooms. They sound better, and are nice quasi-omni-polar speakers. They, like any other omni (true or not), are very picky about placement and set-up. Also, like other omnis, they can create a very diffuse/spread-out image depending on placement. They're less finicky than full omnis (they do not radiate 360* full range), which is to their advantage when it comes to placement and alignment.
For the prices that Vann's wants, I'd say they're not a bad deal, but they're not really approaching full-range until you get into the OMD-28. There are other models I'd consider at $3000 (I'm not saying "would take over the Mirage") - just to be realistic. The lesser OMD model (which is/was a minor update on the OMNI-550) will be fairly thin without a subwoofer (just like their new line-array replacement for the 550).
TBH, I'd get the OMD15 and a quality (non-Mirage/Klipsch) sub; you'll spend less than a pair of 28's will cost you, and have a smaller pair of speakers with better bass extension (even if you go up to $1k on the sub you're still under).
Like this setup:
You could go with OMD28s and the same, but it'll rack the price up substantially (you go from $800 + $800 to $3000 + $800, basically over some 8" woofers). The HK990 is just a random suggestion on a nice piece of gear that was available from Vann's - you can go less expensive:
Or whatever else you have that can provide bass management and amplification for the speakers (or run without a sub if you want to - there's plenty of great 2ch components out there).