I don't know, throwing up some bass traps and absorbers without really knowing how to treat a room could be just as bad as nothing at all.
the thing about near field monitors is that you are close enough to them that what you mostly hear is direct from the monitor. Hence "near field". The room isn't *as much* a factor. Of course, it still is a factor.
With mid fields the room is much more of a factor. And with monitors for full size studios, obviously the room and how it interacts with the monitors is everything.
So, sitting at what's basically an editing station and listening to direct sound from the monitor, I think the money is best spent all going to the monitors themselves.
Also, why wouldn't you go for the Rokit RP 8's, which you can get for that same $400 price tag?
http://www.8thstreet.com/product.asp?ProductCode=22724&category=Monitoring
At $400, other than the RP8 and RP6's, there's also
the Yamaha HS50M. But if it were me and I only had $400, I'd probably go for the RP8 or the RP6. For really close in work at a computer monitor the RP6's might be better, although you would certainly get better bass out of the RP8's. I use the KRK V4 as my small monitors and I love them.