OK you are trying to achieve a couple of different uses here, there is a HUGE difference between playing music in a large room and mixing tracks. Active monitors are usually very directional, they are designed for sitting in front of you pointing directly at your head at a range of 2-6 feet where they create a small sweet spot for you to accurately balance and mix tracks. In a dorm room scenario they will be far from ideal as outside that sweetspot they will sound a little weird. This is why you have speakers designed for studio monitoring and PA designs.
Back on to your topic, you will probably be ok working with monitors for everything, and you need to balance a few things into your decision. Smaller monitors will generally be less powerful but more portable, in terms of size and weight. Large montiors will give you a more full range solution in a 2.0 set-up but will still possibly lack some lower end thump but will generally be loud enough for small to medium sized rooms. A good safe solution if budget allows would be a mid size driver (5-6") and possibly a sub. This makes your purchase decision far more complicated than recommending X Y or Z speaker, especially when we havent even talked about budget.
I am working with some KRK RP6 G3's right now without a sub and they are pretty useful from working at the PC but the mix's dont always translate accurately onto bigger PA systems or indeed when playing though my ADAM's with a sub. Things sound flabby on the sub due to my KRK's struggling with the lower frequencies in terms of accuracy. I am actually a huge fan of the KRK's however as they are non-fatiguing and are a more relaxed listen than some active monitors.
Something worth saying is asking advice is good but you really do need to listen before you buy, or get somewhere with a good returns policy, and consider sending heavy speakers costs a lot of money. Do your research on local suppliers, or even use online forums to find people local to you who may let you see their systems. In just a few years I found literally dozens of people local to me that I often call for a chat, and discuss hardware and software, a good circle of friends will be very helpful in the long run.
I would look at brands such as KRK ADAM PreSonus EVE EVENT Focal and Mackie and make a shortlist of whats in your budget. When you have that short list you can start eliminating options, maybe you have restrictions such as front ported only, or you want to leave some budget for a sub. This is the most important tool you have when mixing and making music beyond you talent and your own ears so its worth spending as much as you can without going into debt.
I am sure DonaldRumsfled will offer some more sound advice and CEL will give you a list of top class sub's should you ask for more help. There is no right answer to this dilemma as everyone's situation is different, I use number of other sites for tech information such as gearslutz.com and homerecording.com where you can ask for opinions from people who may be a but more specialized in the mixing/recording scene.
Edited by Tablix - 6/25/14 at 1:59am