I bought the 901 GM kit. The external controller is ok if you don't push it past 1200W burst. It ran my recumbent trike down the road at 28 mph with no trouble using around 600W at high cruise. controller lasted about 6 months, then it was time to replace it with a Lyens. Smoked two of the FETs so hard it melted solder. It is now a deceased controller. Go with Lipo batteries a Lyens controller with that motor and you should do OK.
05 Catrike Road (Yellow), 20" 48V 1000W GM hub motor,12s24Ah Lipo batt.
12 Catrike Expedition (Candy Purple), 18s32Ah Lipo batt. Lyen 18 FET low RDS controller, C'Lyte HS3540 hub motor, CA-SA, Mueller Bros. Windwrap XT fairing, Terra Cycle Cargo Monster extension. Still evolving, should be interesting by next Spring.
2011 Roll Over America tour, 50 Velomobiles, 5000 Km, 24 days, Portland, OR-Washington DC, July 28th-August 24th 2011, damn I was tired after that.