My room to quite a bit larger than yours and my Sugden 34watt Class A amp powers my 805s and my Sonus Faber Cremonas with ease.
Last week I took my amp and listened to the 803Ds and it played at house shaking levels.
Have not had the volume control past 9oclock position and I like loud music.
The E530 is more expensive for a reason. I was told that because of the design, the highest quality components are used. Rolls Royce quality capacitors etc. They just cost more.
I was very skeptical of the low power rating to so I humped my "power hungry" N805s to the Accuphase dealer, hooked up the E407 and E530. No lack of power, probably more slam from the Class A amp.
I ended up purchasing with the Suden Masterclass, since the local Accuphase Dealer was a dickhead.
Below is a copy of a corespondence from Accuphase when I questioned them about matching the E530 with the Sonus Fabers:
"You do not need to pay special attention to speaker impedance, since the E-530 has an excellent drivability to low-impedance speakers amazingly down to 1-Ohm. My personal opinion, in terms of sound characteristics, as the Cremona shows beautiful musicality, transparent, dynamic and vivid sound, it is much of an excellent companion for the E-530."
Accuphase