If you get an Ebay downpipe get the megan racing, it's at least some what of a name brand and probably better quality, it's not the same as the no-name ebay downpipes and it has a welded Megan Racing nameplate on it. I've had it on my car for two weeks now and no issues with smelling/leaks or any problems, it's also mated to the stock catback and sounds great. Mechanic had no troubles putting it on and said it had good quality welds and it fit great without any issues. It's 2.5" so it doesn't require a reduction to the stock catback.
As others may have said it's not necessary to spend the $700 on a catted DP from an APR or AWE unless you want the expensive metal/high density cats for possibly passing sniffer tests during inspection. The gains are even better on catless anyway. I'm sure the vendors will come on here and tell you different but the dynos don't lie, just save some money.