If tone is very important to you I would avoid the Roland cube all together. IMO, It's fine for jamming at home to give your guitar some volume with some effects to practice with but that's about it.
I've played one show with an MG (long story) and for the "price to specs to tone" ratio It wasn't too bad.
But if you really want a good amp with great tone, don't be hasty in deciding! Save for half a year if you need to :/ unless of course you need one right away...
...Otherwise a POD or GT8 > power amp > 2x12 cab combo will be fine as their effects/amp sims are better than most combo amps. There are professionals that use a setup like that
(Dino Cazares) and it does the job fine.