Priorities...

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.....

@carmenc - the GamuTs are not unnecessary for the Tannoys; their quality is such that they reveal the full capabilities of the Tannoys.
What music do you listen to?

@infection what are your room dimensions?  It appears to me you've received some good advice from others here yet you're still spinning your wheels so to speak.  The Gamuts are unnecessary if you're trying to "steal from Peter to pay Paul" to afford the 10A.  If money is not an object then keep them!  The 10Ts do not NEED monoblock power.  Wanting that power is another issue.  Another way to go is with a tube preamp.  Many options....time for you to determine what's most important to you.

I listen to jazz, classical, fusion, vocals, Spanish guitarists, blues, international music and classic rock.  If you're playing rock and/or orchestral music in a large room, then I can understand your desire for power to control the bass on the DC10t.  Do you really like Tannoy speakers?  Have you listened to others?

Like others have advised, I wouldn't do anything or spend another cent until you've done more research, both outwardly and inwardly.  Good luck.  Regards....

carmenc
59 posts
08-03-2016 1:57pm
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.....

I’m sorry I don’t agree with your statement that Tannoy’s don’t need a lot of power. As an owner of the DMT10 Mk2 speaker my experience shows otherwise. Right now i have these speakers connected to a modest vintage Yamaha integrated amp that outputs 120W/ch in class-AB & the sonics are very good. No issues here. It’s worthy to note that the Yamaha integrated is not a high current amp. I connected these speakers in my reference system which has a very high current amp (’coz it has to drive my Apogee Scintillas 1-ohm version) & I can tell you that the DMT10 Mk2 behaved like a totally different speaker - it just lit up & came alive. I went back & read the manual which has the spec sheet & noted that it’s max handling power is 350W even when the speaker is 94dB efficient. The impedance plot is almost a flat 8 ohms i.e. a very easy speaker to drive.
So, I concluded that Tannoys like good quality & large quantity of power to make them sound their best. On various forums I've read this same thing.....
The Gamut M250 mono blocks are a fantastic amp - my friend has a pair driving the original Revel Ultima Salon in his setup. It’s a pleasure to hear his system each time. The M250 control that Ultima Salon speaker so well - the proverbial iron fist in a velvet glove. From an engineering stand-point what impressed me was that each mono-block has just one (1) MOSFET power output device. Yes, just one!, to create the 250W/ch output. So, Gamut did away with matching many output devices - there’s a compromise in that as you try to match power devices. If they are not from the same lot their parameters vary (that’s just par for the course) & the overall matching & balance is as good as the worst part in the lot used in the amp output stage. With a single MOSFET power output device, all that matching headache is gone.
If I were the OP I would not give up those M250 monos - they are excellent & are, what I would consider, a long-term keeper as they would drive many other hard-to-drive speakers (the Revel Ultima Salons are more difficult to drive than the DC10T).
Stringreen gave some good advice - spend your money elsewhere where you’ll get a better bang for your buck. And, start saving for that speaker upgrade. Another DC10A will come along at a good price. You don’t have to get this particular pair..... FWIW.