Good full range speakers for $150 might be hard to find. And from what I have been reading...bigger speakers are more efficient (ie: easier to drive). If you opt for smaller speakers you will not get the same dynamics as with a larger speaker because of the power limitations in a receiver. Clipping, poping, that sort of stuff. Go for high efficient speakers (95dB @ 1w/1m).
But one thing I have to say is that a good set of speakers for a 2 channel system can be bloody awsome. I have been playing around with my system and have set up a 2.0 configuration just for listening to CDs. No sub, no multi channel stereo.

My floor standing speakers (a little more than what you want to spend) do a pretty good job with the low end (still enough to shake the floor). I find the sub adds to much muddy rumble when I want punch and clarity. My speakers are better for that.
Good hunting and enjoy.