In my opinion, the DB751 is the best sounding amp out there and will make anything sound good.
A have heard several Aggie speakers which all sounded good. I am not as familiar with the Orange, but many people like them. I have used 115s with 210s and really like the combination. The 115s that I used gave a little more depth than many 210s and the 210s were punchier than the 115s. The combination is the best of both worlds, and when it is powered with a DB751, you reach ecstasy, in my opinion.
Requiring identical cabinets has been debated on talkbass for over 10 years.
I liked the 210/ 115 combo. I just don't like carrying 2 cabinets anymore.