>>2688662Yeah, that's a solid price. That said:
buy a used one from keh and get a couple of hundred more off.
If you don't know about them, they are ULTRA conservative on their condition ratings. Their BGN stuff is generally what people sell elsewhere as "like new".
If you don't know what lens to get, why put that much of an investment into it? I don't know your financial situation, but there's likely better directions to go. The 5DmIII is a great camera (not the "best" camera out there, but a damn good one no matter what /p/ claims) so you'll be able to grow into it.
As for what lens, depends on what you mostly shoot and your budget. In general, I'd tell you to get the EF 50mm F/1.4 (the 1.8 is 1/3 the price and a damn good deal, but I think the build quality of the 1.4 is very much worth the price difference, and just how much trash the manual focus ring is on the 1.8 compared to most anything). If you want to play with macro, I'd tell you to get a set of extension rings.
If you're just going to wander around and shoot whatever that's kinda close to you, probably the best lens in the Canon lineup for that is the EF 24-70 f/2.8 (there's an f/4 version too, but if you can afford it, the 2.8 is the way to go). If you think you're more into stuff like wildlife/birding, then go with something like the 75-300mm IS. The IS bit is important for shooting at 300mm. The upper level version is one of the 70-200mm lenses (four flavors: f/2.8 with IS, f/4 with IS and both without IS -- actually like 8 because I think they're on version two now).
I love and shoot Canon myself, so don't take me as trying to talk you out of it, just a "hey, this is a lot of money to plop down on something when there's cheaper, albeit different entry points".