They look pretty good, Jim, but the high Kv may be problematic when it comes to building a reduction drive.
If you wanted to run these motors at full power, which equates to a motor phase voltage of 45 volts, then they will be spinning at 28,350 rpm. These motors seem to be aimed at the model helicopter market, which normally use small, high rpm motors for compactness.
For this sort of power, you are probably better looking at a bigger diameter/length motor with a much lower value of Kv. I don't think I would recommend the TowerPro 5330-10t motors I have, as both have had bad bearings, but they are about the same power rating as the Scorpion you mention, but with a Kv of 215, plus they are less than half the price of the Scorpion. This reduces the motor rpm at full power to about 9600 rpm, still high, but a lot better than 28,000 odd.
Another motor worth looking at is the HXT range. They are still pretty cheap, so may need to have decent bearings fitted, but are about the same price as the Scorpion HK 4025, yet deliver around 6500 watts with a Kv of just 130.
Here's a link to a supplier with a big range of motors: http://tinyurl.com/2k4sw7
Here's the biggest "cheap" motor that I know of: http://tinyurl.com/6bmwd2
. It has a Kv of 130, so at it's maximum voltage of 48V will spin at a much more manageable 6240rpm.