I've done this! Matchless amps are not bad but they do have their faults. I have always found them to be too bright. I suspect that Mark Sampson had been listening to loud amps for too long and the top end of his hearing had gone by the time he got to designing the DC30. They're also over-filtered and run the power tubes way too hot.Buy?
ARE WE NOT DIYers?
BUILD a Matchless, in fact build a BETTER MATCHLESS.
A DC30 is basically an AC30 with too much filtering and bigger transformers. You can swap out the bias resistors to cool down the bias to 100% (Matchless often have the bias at 120-130%!) and your power tubes will run cooler, last longer and sound less brittle. You can reduce the amount of filtering and get a more tactile feel to the amp - you might be surprised at how much more fun it is with less filtering. Look at the Vox filtering to see how. Vox AC30s are possibly slightly under-filtered but the DC30 has so many filter caps it's not that much fun to play.
The bigger transformers are a good idea though. Not good for your back, but great for the guitar's sound.
I recently built a Matchless Lightning style amp for a friend. As I was playing it I started to remove filter caps until it stopped sounding so bright and hard. I had built an AC15 sort of amp not long before and to me it sounded much richer and warmer.
Anyway, back to your regular program...