Quality wise, I think the Tantan TT X21 frame I purchased for just north of 500 USD is pretty good. Im going to just sau its identical to the VB r099. But, it does have it's issues that showed up during the build. Nothing a first time bike builder like myself couldnt eventually handle, but I can't imagine running into the same problems with a frame from a major name brand. I could be wrong, but I don't know that $500 more is going to mean you won't have the same issues.
I guess my question would be, what are you hoping to get for $500 more? I wanted a carbon framed aero road bike I could build myself, something faster and snappier than the aluminum framed endurance bike Id been riding, and well within my modest budget. Mission accomplished.