Priorities...

Again, what are your sonic goals beyond what you have now, what are your sources and ancillaries? Without knowing what these are, as much as we'd like to, it is difficult to make educated/experienced recommendations.

As an owner of Tannoys, you do not need Gamut monoblocks to power them.  Yes, you need some clean power, but quality is the most important factor.  Decide if you want tube or ss.  As for me, I went tube pre and ss amp for my DC8s.  From my research, the 10As are perhaps the "brightest" of the upper end Tannoys. No, I've not heard them to confirm.  A nice tube amp with at least 50 wpc or a ss amp with 100 wpc will be just the ticket.  If it were me, I'd sell the Gamuts, buy a good Integrated amp and get into the Prestige line....Turnberrys i.e.  Good luck and let us know your thoughts so maybe we can be of further help.  Regards.....

Buy nothing until you know it will improve...bring delight to your music.   I would listen to your current system .....go to concerts, enjoy life.

Thank you all for the input.

I will mention again that there is nothing wrong with the sound of my current system; it's very enjoyable. The situation is primarily capitalising on the opportunity of a very good deal but requires a possible compromise. 
I say possible as I may be able to replace the GamuTs with a similar performing alternative. But it raises the question is the DC10A a quantum leap over the DC10T...??
This is where DC10A owners contribute with their opinions of their performance...

@carmenc - are you suggesting the M250i monos are not quality amps...?!

Not at all....just that you have lots of money tied up in all that "big iron" that is unnecessary for Tannoys.  $$$ that could be used to buy a nice quality integrated, which Tannoys do very well with.  For tubes think Manley Stingray, VAC, PrimaLuna HP,  Blue Circle ( what I use, but hybrid ).  SS think Pass, McIntosh, Accuphase, etc.. May need to buy used....that's ok.  That's a key concern, are the 10A's that much better than 10t?  Only you can answer that.

Username "sense63" has had experience with the 10A.  I believe he used a Primaluna HP to drive them.  Try to touch base with him.  That's the neat thing about Tannoys, you don't need to spend loads on an amp.  This is almost a 180 from all of my experience with Thiels.  Good luck.  Regards.....