Had some NHTs a while back,really enjoyed them.Very articulate,excellent focus.If you plan on listening to anything rocking though,very timid.One of the reasons I traded mine away.
You really cant go wrong with them otherwise,definitely a great speaker at the cost.
I haven't heard the SB3's, but I have heard NHT's larger floorstanders at length, both the ST4 and the previous gen. Those offered nice, smooth mids coupled with strong bass and extended highs. Nits? The bass could become a bit flabby and the treble was fairly aggressive. However, one man's "aggressive" is another man's "detailed" so feel free to come to your own conclusions. FWIW, I've read that many NHT owners feel the SB2 is the gem of the SB line so you might want to listen to them as well.
There are a lot of really good standmounts in your price range. If you haven't already, you might try to audition the B&W 602 s3, Paradigm Studio 20v3, JM Lab Chorus S707, or Wharfedale Diamonds. If you already have a sub, Magnaplaner's MMG's might also be an option provided you have the space and a decent amp. Personally, I prefer the Von Schweikert VR1. I won't get into detail because it won't sound the same to you anyway, but I will say that it was the most dynamic standmount I heard by a fair margin. If that's important to you, it's definitely worth an audition. You can find them in your price range used on audiogon such as this one, or if you are good at negotiating, NIB from a local dealer. Trust me, it can be done. Remember what Wayne Gretzky once said: "You miss 100% of the shots you don't take."
Good luck, audition everything you can find, and most importantly, enjoy the ride.