A good S&W can be picked up around 850-950 depending, but isn't really a great way to achieve bang for buck right now. Don't get me wrong about the S&W, I love mine (in fact, wouldn't give it up for anything short of a KAC or POF), great, reliable, smooth shooting fun rifle. Building yourself could come in around 550-650 if you shop it out for a basic M4 carbine style AR with bottom feeder parts. 700-750 would put you into a nice DPMS/Spikes or pure DPMS build with excellent quality but no real bells and whistles.
If you're looking into something really nice and has the "botique" kinda custom feel to it while keeping milspec, Addax Tactical makes really nice uppers in the ~1000 dollar range, often coming with DD, LaRue and other nice branded rail systems already installed. Getting one of those and a Spikes lower (250-ish) puts you in under 1400 for a VERY nice rifle, already pretty tricked out with some sweet toys preinstalled.
My favorite over at Addax is this one for $1025: http://www.adxtactical.com/store/pc/viewPrd.asp?idproduct=1530&idcategory=0
DD Lite 14.0, DD barrel, and DD low profile gas block, good stuffs. A similar upper from DD is around 25 bucks cheaper, but only comes with the plain-jane (rather unexciting in my book, but very cost effective) A2 suppressor instead of the cooler Phantom that the Addax has.
A slightly cheaper by around 100 bucks route, if you don't mind a rounded rail system is the YHM Black Diamond Specter for 899 at Cheaperthendirt. Very nice upper, using one with an inbound Spikes lower for my wife's first ever gun. Forget starting her on something teeny, my wife is worthy of starting off with something that has some grunt to it. A huge plus to this route over the Addax isn't just the 100 dollar savings, but it comes with BUIS included in the price while the Addax does not.