Most definitely active. The hassle of having a seperate amp is not really worth it imho.
At the price range you mention, the KRK’s are great. I’d be leaning towards the 6″ version providing you don’t have a huge bedroom (in which case the 8″ might be a good choice). They are a great compromise between size (not TOO much in your face), and bass reproduction (don’t expect house shaking bass, you can always a single KRK sub when you think the bass is too little for your taste). The 8’s (I think) are pretty big already and the 5’s (which I have) sound great, but are a tad lacking in the heavy bass area.
There are a few articles on other brands/models that are certainly suitable too over on the blog and here on the forums. So (ab)use the search box on both and there is plenty to read on this topic.
An alternative, if you DO plan on playing smaller (house) parties in the near future is to just get two active 10″ PA speakers on stands. Yet another alternative (but budgetwise somewhat higher than you mentioned) is something like the LD Systems Dave G-Series (G10, G12 and G15 I think).
.
