In my opinion u just can't go wrong with valve, as for the valves going it takes a long old time for them to go and when they do it's not major surgery. I was a mark bass user for quite some time but fancied a change and went down the Mesa route and was lucky enough to get a Titanv12 which is twelve hundred watts of filthy valve goodness, I don't believe Mesa make it anymore which is a shame because I would never get rid of mine and paired up with my Mesa 8x10 it's fab apart from my back trying to move the cab. As for size of cab and what head and how much power I find any valve head of a decent calibre will always cut through a mix so much better than a solid state amp. I also play guitar(badly) and have a Mesa mk five and its the same story on the guitar front with valve it always cuts through so much better. As for cabs a four ten is my favourite way forward small enough to fit in the boot but still has forty inches of speaker surface moving air. wattage, anything near the 300mark would be ample for most gigs. A nice ampeg with that warm lovely tone that's like a rub on the back and a horlicks before bed would be a good option 🔊🔊😏