Pima Luna uses auto-biasing and runs their tubes at very low voltages. Tubes should last many years. Any given tube can always go bad of course, but with this being a fairly new amp I'm sure Prima Luna if not the selling dealer, would want to know about it. What did they say?
Yes the power tubes are the large ones. Probably EL34, about as warm and musical a tube as you could ever hope to find. Prima Luna are designed to run with a lot of different tubes though, so feel free to knock yourself out. My bet is after a lot of time and money you come back to where you started.
As far as power goes, that one is even more clear: No, you do not want as much as possible. Why? Granted one of the hardest things to learn, but watts just don't matter. What matters is how it sounds during the vast majority of the time you're not clipping. Which unless you have awfully inefficient speakers (which you said horns, so no way), or crank it really super loud, might be never.
If you want musical, upgrade to a tube preamp. If you want louder, upgrade by adding a swarm bass array (several subwoofers). But I would start by ditching the solid state.
Yes the power tubes are the large ones. Probably EL34, about as warm and musical a tube as you could ever hope to find. Prima Luna are designed to run with a lot of different tubes though, so feel free to knock yourself out. My bet is after a lot of time and money you come back to where you started.
As far as power goes, that one is even more clear: No, you do not want as much as possible. Why? Granted one of the hardest things to learn, but watts just don't matter. What matters is how it sounds during the vast majority of the time you're not clipping. Which unless you have awfully inefficient speakers (which you said horns, so no way), or crank it really super loud, might be never.
If you want musical, upgrade to a tube preamp. If you want louder, upgrade by adding a swarm bass array (several subwoofers). But I would start by ditching the solid state.