I recently bought the makings for a "fat" bike.
I bought a Mongoose Malus which is I believe the same bike as a Dolomite just different colors.
Yes, this is a 7-speed dual disc Dolomite.
I got a 500w 36v fat kit which I will run on the 10ah 12s pack.
Will hold the pack nicely on the down tube.
Since I already have the required packs/chargers.
I will be into a fatty for under $500.
Going with a low power single speed hub like the Strom eh?
Pity. You could have bolted a SickBikeParts 36V kit on for $320 + battery...
http://www.sickbikeparts.com/catalo...ucts_id=180&osCsid=s6t9295jm5d49in5be59vmr0n2
And then you would have an electric 7-speed shifter you can pedal help if you want to, and ride easily when your battery dies as you won't get far on 500W on that bike and you will like having gears to pedal home.
I put a $1K 960W 48V triangle battery in that build and even that seemed wimpy compared to smaller electrics I've built, and it's because of the tire size.
To me the real benefit of a fat tire besides look was running those tires at ~10# for the soft ride, but that is a lot of drag, you might want to inflate yours to 30+#.
Here is a simple test of the drag you can do before you get to motorizing.
Pump up your tires to what the sidewall says is max, 30# on the Mongoose, and pedal out 1/2 a mile on a flat road.
Then, drop the tires pressure to ~10# and pedal back.
Granted this perspective is from a beat up out of shape old man that considers having to pedal more than a mile on a heavy fat tire bike a 'come and get me' call.
The point is drag is drag, your system will be a nice little boost when your great legs stamina get tired, all I am suggesting is feel what's it like on just the bike before you add the weight and drag to it, ohh, and good luck bud, I like silver bikes too ;-}