suggestions on speakers for 5.1 setup $2500 range

expandable in the future, currently with a denon 3805 in a 25x20x12 ft room, windows on 2 sides and hardwood floors- nothing too bright. looking for bookshelves/ monitors- Is it advisable to use monitors from different companies for front/ center/ rear/ sub or would there be integration problems.
any comments on ascend, aperion?