Never had any trouble with Violmart or any of the other vendors I purchased from, the geared motors worked a bit better on the Hills, the problem usually rests with the other parts, sold a Friend a front drive 1000 watter and He converted it to RWD( someway,I forget now) That kit had everything, brake discs,calipers, etc, don't think it had LCD display,Tried to convert an old "Raleigh" gave up in frustration.
The big thing on these kits seems to be the quality of the controller( really makes a difference), to get a DD motor to pull well you need to feed it plenty of Amps, the only weakspot on the DD motors would probably be the sealed bearings( not that hard to replace), you get what you pay for, on the other hand you can over pay.
Justin seems to be a leader in this Field( His prices reflect this) and Kyle Chittuck of "Bolten ebikes", seems to be a good alternative in the USA.
DD motors are a bit quieter and the capacity for regen ( saves the brakes on your Hills) is icing on the cake,I think Justin has developed geared motors with regen capacity built in, expensive, but( big but, no not that kind) well worth it in the long run if you are a serious many Kilo rider.