The models I have liked and have VESA mounting are HP 23tm or the Dell P2314T.
The P2314T has two hdmi ports but no speakers, 23tm has dvi, hdmi and speakers no idea how good/bad the speakers are though.
From what I have seen of it might need a nut and locking washer because the bracket does not appears to be threaded, but that is pretty cheap and available at most hardware stores.
That one does not work for the S2440L you need this one. http://www.ebay.com/itm/DELL-VESA-Mount-Adapter-for-S2440L-/200946180643?pt=US_TV_Mounts_Brackets&hash=item2ec9536223
Tyke supply sells the same curved triple mount linked above.
http://www.tykesupply.com/Triple_Monitor_Stands-Triple_Monitor_Stand_Free_Standing_Curved_Arm.html
I purchased a st2220t recently and my only issue with it is lack of a vesa mount, but recently saw a mod someone did where they use the stand to clamp onto metal plate attached to a mount and seems to work well.
It is a good touch screen as long as not expecting more than 2 finger touch which...
My GTX 670 will only show post screen on 1 screen at a time when plugged into multiple monitors, even if one of the displays was off it was defaulting to it till I unplugged it.