Honestly, a good bike will not get you anywhere farther if you shell a grand on it. Many friends I had did just that and ended up spending the price of a brand new bike in repairs.
My best friend has a 950$ bike that broke too many times (and cost a lot to repair) while I rode the same ugly old bike for two years. On top of that, expensive bikes are often stolen.
On the other hand, you could buy 3 normal bikes with the same money and they are much cheaper to repair (if you don't do it yourself). Remember: it's only wheels and a frame, nothing worth the price of a beater car!
Just avoid SuperCycle. These are made to look like mountain bikes but are extra heavy and break easily. I'd also recommend you to avoid trigger-like speed changers, not because they don't work, but because they are a pain to adjust when they're not calibrated.
Disk brakes are not necessary unless you plan to go extreme with your gear. Spend 300 bucks on something generic but solid. If it's cheap, return it, but for pete's sake, don't get yourself a 900$ mountain bike to go to work!