On the gas side, I think the Marsal MB is either the best brick oven available today or tied for best (with the Y-600 with the brick ceiling option). Last time I checked, these are shipping with fibrament hearths, which I'm not sure I'm in love with, because fibrament is so physically and thermally fragile. Fibrament is also a poor conductor, although, in this instance, that lack of conductivity might be a good trait as it slows the bottom bake down and allows the oven to be run at a higher temp, which, in turn. gives you more top heat (increasing top heat in gas ovens is usually a good idea).
Marsal will give you firebrick decks if you ask for them. Firebrick can vary, and, so far, no one in this forum has experience with both the fibrament and firebrick versions of this oven, so we're flying a bit blind, but, from a theoretical standpoint, firebrick will give you many more years than fibrament and should have a relatively similar conductivity, so I would probably go with the firebrick.
Regardless of what you choose, the Marsal is in an entirely different class than the countertop you've been using. This will be like going from a tricycle to a Ferrari.