@mesch : my Sugden isn't an A21, it's a class A/B amp so it doesn't get hot at all... my two top contenders are the Croft and the Belles... which ever comes first on the used market, but I rather get the Croft because it's only 40 watts/chanel and I don't need more then that...
Here's my advice for you. I wrote it before realising you didn't have a pair of speakers yet, so it may be useless :
I've had 2 pairs of Tannoys (Belvedere + Arden) and they are a lot easier to match then my Altec... never heard the Sterlings but they must be pretty good... with 91 db efficiency, you could use a bit more power then I do... based on your Tannoy (I never heard the Esoteric MG-10), I'd go for a Belles integrated (75 watts/chanel)... from what I read, to better this, you have to get a class A (Pass labs, Sugden A21, First watt), or go with tubes... the AVA set 120 is also a good choice, but less powerfull... As for the Sphinx, I read a very informative thread on AG comparing it with the Belles and the Belles clearly won...