All you need is something that is accurate, but mainly - something that you get used to.
People say "you can't mix on home stereo speakers!"
well, that isn't exactly true. If you know all of the quirks/deficits of your speakers, then you can mix on them. (for instance, they boost the bass significantly, or accent very high frequencys kind of harshly) whatever..
Then you mix your stuff accordingly. So, you goal is make it sound "bad" on the home stereo speakers, more or less...to get a stable mix.
Same thing with monitors, except that on a decent pair of monitors, you should be able to mix it until it sounds good on those speakers - and then it should sound good anywhere (lets face it, the deficits of a lot of home stereo speakers are what make them rock!)
So, if you find monitors in your price range (all the ones that you mentioned are good)...then you will be able to get great mixes out of them easily - once you have listened to a lot of material on them and figured out how a good mix sounds on them - that's the deal with mixing on *any* speaker.
And thats why engineers are slow to give up a speaker that has been good to them

(a la Yamaha NS10).
The 800 dollar ones that are "bad" normally come down to stuff like limited bass response...or, "ear fatigue" from harsh frequencies (that's a legit concern). But, you can still get good mixes out of them.
It's more of a jump in and do it thing, with monitors. Whatever you get, you can learn to use and be happy with. Researching the numbers doesn't gain you a lot...go listen in person, make a decision, start learning to use them.