The Onkyo 818 is a THX Select2 receiver, which means it will reach 105dB peaks in a given room size (2000ft3). THX Ultra receivers will reproduce 105dB for a period of 3 continuous hours (3000ft3 area).
From experience, I know that receivers at the price point of the 818 won't properly drive and maintain control of satellite (bass limited) speakers like the Miller & Kreisel S150's, which are a 4ohm rating. The cheapest receiver I've found to do this is the Pioneer SCLX83 and SCLX85. I doubt very much Onkyo have been able to replace an already competitive £1k receiver with the higher current amplification of the 3009, AND include Audyssey's XT32.
I'm not belittling the 818 though as its a cracking product for the money, and to include XT32 at this price point elevates it above much of the competition with ease. But we have to be realistic about it's ultimate abilities. It's a £1k receiver, which is likely to be used with lifestyle sub/sat packages, and, in my opinion, is ideal for the likes of Monitor Audio's Bronze AV packages, and KEF's Q series AV packages.