Furnace will not fire up

I am looking to replace my existing GAS furnace for my 2 story home this year. I have talked to a few companies and here's the story I'm getting. My Trane guy is telling me to get the XV95 because the variable speed motor will help my 2 story home. Actually the problem I have is that the bedrooms on one side of the 2nd floor are colder in winter than the other side. I don't see how, but he says the variable speed helps that. ALSO, I may have to replace the A/C unit in the future and he says it is IMPERATIVE to get a variable speed blower because the A/C will require it. [B] Is that accurate, and applies to all brands?? [/B] Because I priced out another brand and they wanted to give me the non-variable speed blower motor and they knew I might do my A/C in the future, too. He offered the variable speed as an option, but the cost was considerably more. Also, do I need a new t-stat with the XV95 because it is a 2 stage? Would that be a DIY option? Because we did just put in a programmable t-stat a few years ago. I'm also a little worried about the condensing aspect of the furnaces, because this is in the attic. One neighbor said he had one that wasn't installed real well (I guess) and the water was not flowing out properly and he was getting shut offs. What should I check on to make sure the condensing unit is installed right? The million dollar question, of course, is which brand should I get? ;)

I have a 2 zone system, and one zone is not working. When I set the thermostat to heat, clock motor turns, and the tab appears to depress the micro switch completely, but furnace does not come on. If I depress the micro switch manually, furnace comes on immediately. Thoughts?