It all depends on what the rider wants ofc, some may not want a more powerful system preferring instead no more than an assist - however generally speaking I must agree with rudyauction509, that with some shopping around you'll find far more efficient ebike systems for the same price, less if you wish no more preformance than what's linked.
They're out of business now I think, but I had a 12v 'Zap' electric friction drive virtually identical to the "The Powerful Hill Climber Dual Motor Kit" advertised and to say it was an underwhelming disappointment would be an understatement... and I paid nothing at all for it lol
Just for reference, 1000 watts = 1.34 horsepower (mopeds typically 2.5hp & up), so if that's 100 watts (can't tell, no specs offered) it's
0.13 horsepower - hardly enough to warrant it's own weight & with a friction drive & tiny SLA battery, it won't do it for long...
BTW, if your shopping for ebike stuff and the merchant offers specs for their product, calculators like the above & this can be handy to get an idea of what's offered if you've not seen them before (watts to horsepower & volts/watts to amps, amps = amp hours for estimated range etc);
http://www.rapidtables.com/calc/electric/watt-volt-amp-calculator.htm