one of the problems I've seen with Alesis monitors is that the tweeter likes to vaporize if you just sneeze. To many monitors made by them seem to fail awfully easy. The cheapie monitors ones by Alesis are "ok" if can pick up a pair for
zilch...but don't expect them to really last because of their durabilty.
The monitor 2's are just a bigger version, same problems (not to mention a lousy low end reproduction), and for that price range, there IS much better to be had. I'd get yourself a pair of $75 Auratone cubes [used] somewhere before I'd get some of these "bargin" nearfield monitors... ..and Auratones are supposed to simulate a TV speaker!..but actually sound pretty good for what they are...and you can't get much smaller. I don't think they are made anymore, but awhile back, you saw them sitting on the meter bridges of just about ALL the studios on the planet. They are great for "checking" mixes and I even think for checking bass volume and stuff like that. They are really kinda supprising speakers for what they are. But then, many will say they sound like crap like the popular Yamaha NS10 speakers. (I had a pair just long enough to realize I REALLY didn't like them though, unlike my Auratones).
As far as headphones for mixing. I've done a fair amount of it myself and have gotten results that were acceptable enough to me. I use the [bass heavy] Sony MDR7506 phones mentioned above for $100 at any decent store. Do I mix better with speakers...?..in most cases yes, but I HAVE done some mixes I thought worked out OK with just using the cans. I know many disagree with mixing soley on cans, but I feel I know the sound of the MDR7506 pretty well at this point (infact I have a half dozen pairs and one pair is a definate favorite over the others...no one touches them but me!), just like I know my speakers. I have probably about $3500 wrapped up in my speakers if you were to replace them, and I think that the Sony headphones do the best job of emulating them. Infact, I like using the headphones for hearing noise problems, editing and stuff like that OVER the speakers. But, sitting in the sweet spot of my speakers by far is better if I had to choose...mainly because it makes it MUCH easier to make mixes that translate well over other systems. Also...being the rookie I am!!!... I like to use A LOT of reverb on many of my mixes..and it is much easier to make decisions on speakers with the amount of reverb. If I am just recording some synthsizer tracks and DI guitars, etc...that stuff is pretty much just samples anyway, and much of the "critical" decisions have been made as far as sound....to SOME degree. I can lather a solo instrument with a reverb in the cans and it will sound great...but the speakers say....eh...no no!!
If you only have a couple bucks and MUST use headphones, (because of neighbors, late night recording..etc) just realize the limitations, but don't think you can't to use them to get decent mixes. VERY finished mixes...that's another subject. Go to your local Guitar Center (or wherever!) and try a couple pairs and see what you like best... About 75% of the people seem to favor the $100 Sonys it appears for THAT price range. Anything cheaper, you might as well buy another set at Radio Shack for $25 that sounds better than your current ones.
But...take your ears...something you've recorded if you can, a favorite CD, and see if you can listen thru a variety of things with these sources. It may be an eye opening (and ears too!) moment for you.
). 
That's ok... I don't want to particularly deal with 8 people sitting in my control room either all offering suggestions either.