Biggie, Congrats. We haven't ran too far amok. I still say you need to test a PowerTan machine with 'your' controls.
I have used a tree spade and the 'scraper' tree spade. With the scraper spade it was about 50/50 on the success rate, some of the trees were too big but they were going to get dozed so we tried using it.
They make 'pods' around here that you can use the tree spade to set them in and then go to the new location. For 500 trees it may be worth setting something up like that. One bad thing is the size range on the trees, hard to get it all with one size.
Here for $100-120 they will plant a 5-6' evergreen.