Dan,
Gotta say that $850-950 to me is a lot for mobile head planer. I wonder if you would consider the mobile feed table instead..like the G0453? I use a similar grizzly planer to the 453 and love the quality. Additionally, there will be a point where consideration on a helical head comes in. The G0477 can't be upgraded to my knowledge.
I'm in the market for a planer and I've been looking at Grizzly's G0453. It can be upgraded. Grizzly offers three different helical heads for that model. It's actually less expensive to order the straight-blade planer, then install the new head, then it is to order it with a spiral head.
Pete