Doc, the Marsal MB 60 will give you a more even bake than you have now. And it will give you a faster, more balanced bake at higher temperatures, which some people prefer.
If all you're looking for is more even browning to the bottom of your pies, and less water from the veggies, then an $8K Marsal is probably overkill.
First, it sounds like you need to investigate the stones further and look for the notch that Walter is describing. If you have the original stones, great, if not, you might want to start looking for a set of original stones for sale. If finding original stones proves fruitless, you might want to look into either fibrament stones or whitacre greer firebricks- both offer low conductivity and even heating.
I would also continue to investigate the condition of the burner. It's hard to tell from the photo, but it looks like some flames are burning brighter than others.
Second, if you don't have an IR thermometer, get onehttp://www.amazon.com/dp/B00837ZGRY/?tag=pizzamaking-20
and use it to measure different areas of the floor. That will go a long way in determining how evenly the floor is heating.
As far as veggies go, if you're making NY style, I highly recommend taking a page out of the NY playbook and both keeping the number of toppings to a minimum, as well as going very sparsely with each individual topping. Both onions and green peppers should be sliced into long, thin pieces and distributed sparsely (ie, you shouldn't get an onion in every bite). Mushrooms should be sauteed briefly before adding to the pizza to drive away some of the water. Piling ingredients onto a pizza works for longer baked, drier, thicker American style pizza, but it's the kiss of death for NY. For NY, less is always more.