I have read "reviews" from people who supposively have both the HPI and the knockoffs, and they claim that they are very close in quality, and that HPI parts fit the knockoff.
I forget what parts specificly, but there was a line I read to the effect of..
..."all you need to do is replace the _____ with the HPI one and there is no difference between the two that I can tell"
but keep in mind....
...these "reviews" are always written by people selling the product....
I contacted the seller in FL and asked about picking up the buggy to save on the $85 shipping costs, and he said "we're not set up for that"

whatever that means.
I assume he has them shipped to you direct from china then.