Man, tough crowd. Brother came in here for some help. If you posted this question here, I think you've already made up your mind since you know none of us will talk you out of it. Hope your wife doesn't kill you.
I started this hobby with a 10. 10 became 55 in less than 2 months. I bought a house and 55 became 90. I didn't like the way the guy who built my tank designed the top and the over flows, so I got rid of it. 90 became 180. My sump went from my stand, into my basement. I just built a frag tank and added it to my system THIS WEEK and I already want to make that bigger. We're bad.
If you don't have a chiller that can handle a 140, I would consider waiting until after the summer to upgrade. It would suck to stock the tank only to have die-off due to heat. As other members mentioned, bigger tank = bigger skimmer, bigger chiller, more lights, flow, electricity, etc.
I don't know much about the structure you live in, so I can't comment on the strength of your floor. Just keep in mind you will be adding a minimum of 400 pounds.