I would have used equipment that carried the most amount of pax and still had relatively low turn-around times. CRJ is way too small for a route like that. The route is also so short you're going to make a ton of money even if the plane you're flying is not economical fuel wise. Slots are going to be expensive, so don't choose CRJ.
The best aircraft would be A321-200 or B737-800/900, but that's probably not realistic. I haven't checked your current fleet, but like others have said.. there are alternatives, like the MD-90.
And don't be afraid to pack your plane full of HD capacity seating to maximize profits. Pax don't care much as long as the flight is less than 3 hours or so each way.