If your current bike in on the small side I wouldn't invest to much into it (although I would keep it as a spare for now). You could probably score a similar bike off craigslist in your size for a fraction of the price of some of the bikes you listed.

Many mid 80's to 90's rigid MTB's had beefy frames, stable geometry, ability to fit wide tires, and eyelets for both racks and fenders. To commutify it get some slick tires, add fenders and a rear rack. On top of that you can add bar ends for more hand positions or a trekking bar.

Depending on your area figure about $150 for the bike, $35 for a rack, $35 for fenders, $40 for tires, and $20 for bar ends. You could basically outfit your bike with equipment more suited for your purposes for close to 1/2 the price.