Dali has a wide range of speakers, I'm not sure any dip down below US$300, but I think one or two of them come near.
Elac -- definitely worth checking out.
Mission, I think has some pretty good ones in that range.
I'm not sure Totem has anything in the <US$300 range, but if they do, you should definitely put it on your short list.
I've heard good things about Scandyna (ex-B&W, I think), their MicroPod is <US$100 each, if you can find a distributor.
Dynaudio (my current speaker company of choice) don't make anything that cheap, and even so, I haven't heard good things about their entry level gear (I think I heard that here, too).
I think the very entry level speaker from Focal (Chorus 705) might be in that range, but again, that's their very entry level, and I haven't heard it myself, but I like their whole range, so it's worth at least listening to, methinks.
Or you could just buy a pair of Visaton B200's and put 'em on a board ("dipole"...no, wait, that's "open baffle") and be done with it. You can think of them as big ol' headphones that you don't have to hang from your head.