I began researching ebikes about 2 years ago and it took me a good month and a half to decide what would be best for me. Even then I didn't get my kit until last month and have only had it installed a little over a week. I went with a non-hub motor for the torque to get me over a big hill but since you said your commute is flat I am wondering if you are looking for speed or for convenience. Your commute sounds pretty mild and you could probably get away with a 200W hub motor and some SLA batteries. Sure you won't go 25 mph but it will get you there without breaking a sweat. Since you are looking for a hub motor I also advise looking local. You're more likely to get a deal and you get the support of the dealer. $450 should be easy for a setup like that but you definitely need to do your homework.