What's your budget? People rave about the Mackie MR5 MK3's, but I had a hard time getting bass to sit well in my mixes with them. If you're looking in the "affordable" range, Yamaha HS5's sound pretty good, but you can get the HS7's for about $140 more. I listened to the Eris E5's a few months ago while I was shopping. They sounded pretty good / flat and they have a front port.

If you're looking in the high end range, the Adam A5X's are amazing.

As far as tone, you'll want your monitors as flat as possible for mixing. Exaggerated hi / mid / low are a nightmare during mixdown.