I think the 20/20 is great for it's price. As for tone, yeah it gives more warmth to my Solid State preamp (blue head) than when I play at a friends house using his Solid State power amp. As for loud, well the off position is at about 7 o clock position, but i haven't gotten past the 9 o clock position ever! in other words it ungodly loud, but I can't answer for how good the tone remains at louder settings.
The Marshall cab was part of a JCM900 combo, btw. A friend was in need of money so he offerend me the 20/20 + Cab for $500, ahem I like my friends