B&W Nautilus 803 or B&W 702 S2?

Of the 2 B&W Options my pick would be the new 702 S2. I would also pick them over your Paradigms. If you haven't listen to them be sure and do so first to make sure you like them more than your Paradigms. 

All the D series B&W's are more efficient than the older N and S models. One of my favorite systems I sold to a client of mine was the 802D2 on a ARC Ref75 which powered them just fine. I do agree somewhat with hifineubee that the S and N series B&W needed series power in order to make them really sing properly which is why I mentioned my choice of the 702 over the N803. Your current A5 will do just fine powering the 702.