I am dying to get a system to help make my manual chair easier for me to use (c5-6). I am in my power chair most of the time but when I travel (3-4 times a year) I use my manual and I could really use the extra boost an e motion will give me or something similar. Of all these type systems which do you like best and why? How much are they new? Where can I buy them from? I saw on ebay (thanks to the wheelchair post it never occurred to me to look there) that there are a few sellers with used ones. What do I need to know before getting a used one? is there an ebay seller you trust for used equipment or one I should completely avoid? Thanks so much for your help!!