Thanks for all the opinions so far guys! I had a look at thiele cabs, I've also got a book (remember books!) that has tutorials on how to make different cab types and thieles are in there - very complicated! Again though I didnt really want to add another cab to a combo that shouldnt really have any issues in this price bracket.
Yesterday I took it round my mates house (the one who's the tech) and he had a look inside the chassis with me... First of all I must say what beautifully designed and made these amps are, so neat, tidy and well thought out and built, top marks to Mesa for that! We looked at that first cathode cap and its 10uf, which is about mid-value acording to him, so that shouldnt be the problem. Then, my earlier theory was completely blown away when we plugged it into one of his marshall 4x12"s... Bloody hell! Instant big fat bass response, and an awsome old school metal chunk/crunch sound that I have never been able to get, also beautifully warm yet sparkley scooped fender type clean tones also... and everything inbetween just had more warmth, deep bass, and presence.
Now I know what your all thinking, its going into a 4x12, of course theres more bass!... But having tried that big open-backed 1x12 at the start and not heard much difference I just assumed there would be only a slight difference with a 4x12, but the difference was dramatic. Also, my mate said that 4x12s arent actually all that efficient at producing bass response, and their perceived bass is more to do with the amount of air they are pushing. His advice was to either get an efficient closed back 1x12 extension cab (a thiele for example :wink: )... or sell it and get a 5:50....
Oh well, anyone interested in a mint 5:25 10"?