Hi NeilH!
I also own SF Electa Amator II as fronts and Signums for surrounds. I started with the Signums as fronts and then upgraded to the EAII. During this upgrade I tried other speakers from JM Lab and Dynaudio, but the EAII came out as winners. They are, to me, wonderful speakers for Stereo as well as HT use.
They do require good amplification, though. I have TAG 100x5R which seems to have no problems driving them in my 20m2 room. A safe choice would be, as Lowrider suggests, Bryston amps.
I dont quite like de SF Solo center and while there's no other options from SF, I'll have to keep my JMLab Electra CC900 center.
My sub is a REL Strata III. While the Gravis is a good choice, I found that the Strata III (or even two, if your room requires it) stands out as providing more value for your money.
Regards,
Nuno Santos