If you're looking for BftB, you're looking primarily at Behringer Truths, JBLs, KRK, M-Audio, and probably topping out at a 5" woofer.
If you can find a set of JBL 305s on sale, they are decent for the price. I think I paid $210 for a pair. You won't get a ton of low end from them, tho. For that you'll be better getting 308s. I wasn't impressed with the M-Audio BX8s, I thought the bass was somewhat bloated. I've also got some Samson Rubicon 8s with the ribbon tweeters but those aren't made any more.
Look for some used monitors. I really liked the Event TR8s years back. They were about $500 a pair retail, so if you can find a used set, you might get them for $300 or less. I got my JBL 308s used for $325 on Craigslist.
You might also listed to some KRKs. You can sometimes get a decent deal on those from MF or GC.