You have a tone knob on the bass, right? Use it. As the strings wear in and get duller, turn the knob back up some to keep the tone where you want it. If you don't want to use the knob on the bass, but can cut highs in the amp or a pedal, instead, go for it.

Yeah, the increased tension takes some getting used to (flats at the same gauge, scale, and tuning tend to be tighter than rounds). I remember mine feeling particularly "hard", for want of a better term, after I switched. Less "sproingy". And, yeah, they'll feel harder near the bridge, though the actual tension is the same at all points between the nut and bridge saddle. You just have a lot more leverage with which to deflect the string near the 12th fret than you do near the bridge.

If you haven't gotten the instrument set up after switching strings, you ought to. Or at least check to make sure it miraculously isn't needed. Such a change in tension can change neck relief and/or intonation.