I have the A5 Int, and run B&W CDM1NT bookies.
A good pairing; the B&W's respond well to the grip and grunt of the A5.
I too like scare the neighbors from time to time - the A5 has the power to keep it clean.
Let the B&W hate begin.....
I can't see the A5 as a good choice. I used to have one. It does have a lot of power, buts a very forward and aggressive sounding amp. It takes the concept of PRAT way to far. All attack and no body. That's the last thing your speakers need. A higher end NAD would probably be a good choice.Also have a look at Marantz or the new Parasound Halo integrated.
That’s what makes this hobby so difficult -everyone's 'end result' experience is different.
There isn’t one review of the A5 that describes it as forward or aggressive, nor has it been my experience.
The advantage of either as a used buy will be the ability to flip it back with little/no loss which affords the user to get direct ears on experience. Both will hold their value in the short term.
I also have used an A5, and not going to disagree with what sfall heard in his system, however in my system it was not overly forward or aggressive. IMHO, I think the A5 would be a better choice than the Sphinx. The Sphinx is rated for 200 watts into 4 ohms, however Stereophile's measurements found that it clipped at 155 watts. The demanding load of the 804S will be too much for the Sphinx especially since you like to play it loud.