I personally own an S23a750d and love it. When researching my purchase, I couldn't find much of any difference between it and the s23a950d aside from the stand design and the price. I was able to snag mine for 350$ (and it went on sale pretty frequently all through last fall and early this year). It comes with a tridef 3d license as well.
I would definitely make sure to get a monitor with display port, so you can take advantage of the full resolution and framerate, and the s23a#50d (whichever one) has that. Make sure you order a proper cable for your monitor as well, most have display port - display port cables, but my 7870 only accepts mini display port, so i had to wait an extra (painful) week for that (nobody in my area carries the cables, their not very common yet).
edit: After a ton of looking on cables and adapters, I just bought a cable that was display-port-male on one end and mini-display-port-male on the other.
3d is great!