I could not be happier with my 6040. The loaded tires help esp. when working 3yd. Duribuilt scraper. The ATI 4in1 bucket is handy. MINIMAL down time in 300 hours.
The kubota M40 tractors are excellent, I recommend you consider the 4wd and hydraulic shuttle.
Also, I would not be concerned about not having enough weight; the M7040 4wd with cab weighs about 5500 lbs, with the FEL and a bucket you can probably add close to 2000 lbs, fill the rear tires probably adds something like 1200 lbs, and you are up to about 8700 lbs. Add an operator, cast rear wheels/wheel weights, rear implement/counterweight and you'll be pushing 10,000 lbs.