hmmmm tough questions, i just bought a JMP 2203 '78 Marshall 100w lead series and love it. I don't use it for ditortion. I get high gain out of floor pedals use the marshall as a
power amp and boy does it have volume, craps all over my peavey 5150 II 120watt head.
So maybe concider keeping the head but purchase a
distortion pedal or something. You have a great amp.
To sell it.......well i don't really know about Belgium but here in Australia they go for around $1200-$2000 Aus.
There is one for sale on ebay.com in the U.S. so watch that and see how much it goes for.