Valves are not expensive, and they don't last forever. Try buying a selection of valves. Some combinations work very well, some don't, and what works and doesn't is very personal.
For every person that cites running a 12AT7 in V1, there'll be another who thinks the 12AT7 sounds flaccid and dull. For what they cost, try a 12AT7, a 5751 and a 12AY7 in V1. You can always go back to a 12AX7 if you don't like it, plus you'll have a roster of valves to admire. What's not to like?
For the output valve, it comes with a cheapie as stock. They're OK, I guess. Some like Sovtek, some like JJ, some like the Sino EL84 from Ruby. After a couple of years use, just about anything will be an upgrade.
Then there's the Russian NOS 6p14p. I like the 6p14p, you may not. They're cheap enough to play about with. They have a different sound to them, and a different compression characteristic. Last lot I bought, I got four for the price of one JJ. They all work too, which is nice.
You may be tempted to clip capacitors out of the circuit, or swap component values around. Before doing that, try turning the amp up, and your guitar down. Try an EQ pedal. Use the guitar tone control.
I had an AC4TV10. I didn't exactly bond with it, but good sounds could be had with a 12AY7 in V1, a JJ in V2, and turning the guitar down and the amp up. I gave it to one of my Sons, he seems to like it.
Thanks for the advice, I have just bought some valves, though they don't seem to be so cheap (well not for me) here in Australia.
Local supplier suggested I try a JJ ECC823 (hybrid of a 12ax7 and 12at7) to replace the 12AX7, and for the power tube a JJ EL84. I found some instructional you tube clips which will be handy.
Found some other mods on clipping / changing capacitors but may wait to see how the new valves sound. I agree in that its best to use the amp and guitar tone control to roll of the highs than taming them in the circuitry.
On another note, just ordered a Celestion Alnico Blue, so pretty excited to see how that all pairs up. Now need a cab to put it in....question for another forum.