Let's see: your criteria is good mileage, has to look good, reliable, lots of power, lots of room? And you are male and not that old. So can you afford the insurance on anything you buy? I mean more than just liability insurance? Assuming yes, you have few choices that will fill your criteria.
Power and mileage probably are not going to happen if you want "at least a V6". Of course, if you feel that 18-24 mpg is good mileage, then yes, it could happen with the right car. Also depends on your definition of "power".
Of the three cars you listed, I would say the Monte Carlo is your best candidate. Don't buy the Charger. Chyrsler is going under, that is certain. When that happens, good luck finding OEM parts for your car. And a Charger will get very poor mileage and the styling of the interior is out of the 1970's. Their truck division might get purchased by Nissan, but outside of that, you can kiss the company good bye.
The Tahoe could possibly fit your needs if you can put up with the mileage. It would probably be the least expensive to insure. If I were you with that criteria I would look at Honda/Accura, Nissan or VW.