Fit is definitely important (small class size, LAC-feel), however some of these schools are ranked lower than Northeastern in CS (Tufts and even more so Brandeis) and are less selective than NU overall.
Here is the graduate school CS rankings from US News. (http://grad-schools.usnews.rankingsandreviews.com/best-graduate-schools/top-science-schools/computer-science-rankings) There is no undergrad rankings, but this will give you a pretty good idea of how the non-LAC’s stack up against each other. NU is 60th, Case Western in 70th, Tufts is 70th, Brandeis is 82nd. Harvard and Brown are a clear cut above the rest at 18th and 20th.
In terms of overall selectivity, Northeastern is #35 in the country in terms of SAT/ACT average selectivity (1390, 31.5). On your list that puts them above #59 Brandeis (1350, 30), #66 Colorado College (1325, 29.5), #51 Oberlin College (1362, 30), and tied with Vassar (1390, 31.5).
(http://www.forbes.com/sites/schifrin/2014/08/04/top-100-sat-scores-ranking-which-colleges-have-the-brightest-kids/)
I am not suggesting you get rid of these school, but if the point is to go to a school that is a better fit and also a better school in generally it might be worth setting your sights a little higher.
I am surprised there havent been more mentions of RPI. Thats seems to be a great fit for you in terms of strong CS program, ability for you to get in, and more intimate setting. Cornell would also be significantly more in reach (and better at CS) than some of the schools mentioned.