$300?
Save up for a couple more weeks and get the 8" fostex for 499$. They sound *almost* as good as mackies, and the difference from a 6" to an 8" woofer is pretty impressive... $300 wont get you very responsive monitors, but if thats your total budget Id suggest going to a store that sells different monitors and listening to find which ones sound best and will fit your budget.
Edit: mackies are $479 apiece.