If it were any modern type, SS or such amp, I'd say drop the thing, but a quick google seems to make it an all-tube and not only that, a p-t-p amp. In which case I would NOT sell it but keep; those things can withstand a nuclear apocalypse, literally. You might never happen to own one again.
50W is a bit much in tube amps for many a situation, but it depends on a lot of factors. My Ceria is 36W with an option to run in 18W and 18 is just way too little. 36W is pretty much perfect, I play it the loudest it goes without starting to sound ugly and it's just perfect volume for playing in a rather large band. I use a 4x12" with old 25-35W speakers which probably aren't the most efficient - it'd be much louder with, say a V30 or some other modern speaker setup, but I like the soft midrangey low-wattage type much better.
That said, I have dreamed of also getting a 50W marshall head to use just for leads...because at 36W I really can't get my leads loud enough when everybody else is also playing at full volume. As I said, it depends on the sound you want and the speakers you want to use. I could get my 15W amp loud enough for leads, sure, but at that point the sound was far from perfect IMO.
Anyway, stick with it is my feeling...get some inefficient speakers for it, or like maybe an extra 1x12" or something...OR, remove it from the chassis and build/buy it or have/make the old chassis into a head format, which would make it much easier to use with different cabs, use an attenuator...the last one is what I'd do myself since I love to tinker stuff like that, I once converted a 20W Marshall combo into a head...
I don't think 50W is too much, it's more like just the perfect power rating...you may need some tricks often to keep it quiet enough, but when you need power it's gonna be enough for everything.