It will help to go fast on the flat but will really struggle up that that large hill.
The DD hub is a fast 470rpm wound motor for cruising, show it a hill and it will struggle it is a non geared hub which has no internal gear reduction for hills.
A geared hub although less power wise in watts has internal gearing reduction to enable it to cope with going up hills at a lower speed then on the flat but pick the correct hub and it will get you up the steepest of hills. You have to weigh up out right speed against climbing abillty but don't be swayed by power alone as you need a hub wound for the right speed.
My 250w 270rpm geared hub tops 24mph @36v at 48v it will be nearer 28mph at 36v the range is only 20 odd miles but at a average of 15/16 mph I can get near 60 on a long ride.
But hub alone is not the only thing to think about it needs to be couple with a controller and a decent battery.
What makes a hub motor the "right" motor? So having gears makes it suitable for hill climbing, but compromises speed on the flat? That makes sense, hopefully I got it right. Also, where do you guys suggest sourcing an ebike motor? eBay rarely says whether it is geared or gearless, or any real useful information. The hub motor I was originally looking at was a 1000W gearless motor, so I guess thats out of the picture now.
My requirements are a max speed of around 25mph and ability to climb hills, and preferably a range of at least 6miles. I guess the range entirely depends on the battery but I still thought I'd add it in. Will a 250w motor achieve this for me? Was the 1kw overkill? Can I buy this kit on eBay (or elsewhere) for <£250?
I'm very sorry if it seems like I'm having you guys do my research instead of doing it myself, it's just I thought that the 1kw motor I had in mind was perfect and only now have I found out it is not. I really do appreciate everyone's input