Hi lee.pie,
Welcome to the forum, you have come to the very best place to get advice and recommendations.
A couple of words of caution first, I note that you are interested in a 1000w system/kit this would be illegal to use in the UK (if you are from the UK) except for off road use on private land. It would also be very power hungry and drain batteries very quickly thereby giving limited range.
Now we have got that out of the way, my completely biased suggestion would be to fit an eZee conversion kit. eZee are renowned for their high torque motors, reliability and good value for money.
Something that might be of interest to you is that they can be de-restricted for off-road use.
Cyclezee are offering special deals during the month of July to Forum Members, so send me a P.M. or contact me via my website if you are interested