Pay off mortgage or invest?

[John Dersoe]

I am in process of selling in NY. After mtg paid, commission, taxes, cap gains, etc.. I'll have +/-425k left over. 

My new 30yr mortgage in Tampa is 1600 a month. 324k total. My monthly income is around 8k.. BUT, my bills top out at around 7-7.5k. Not a good feeling to almost be right at what you earn. 

Would you guys use 324k of the 425k left over proceeds to free up 1600 a month and be mortgage free for extra cash flow? Side note.. I already have +/-700k in various investment accounts. So my real question is, at almost 50yo, would anyone prefer to be mortgage free with a nice monthly cushion between income and bills or use the proceeds from the sale for something else?