Passively bi-amping

If you go active, you can get some monster power(Sunfire 600 for example) for the bass and leave Aleph to do the rest of job.

B&W X-overs even on flagship models is not the best you could think of. Adding an electronic X-over(bypassing or removing the built-in one) will give you more flexibility to get from your speakers the best jewels without breaking the bank on a pair of x250's.

One Aleph 5 is definitely not enough to power-up 802's and to be frankly not even enough both of them to open 'em up despite how great they are.