I can't speak about any other dealers/websites other than DHGate, because I have bought from it (indirectly). One wholesaler to be specific.
I have a friend who Deals/resells watches/shoes etc... from a DHGate wholesaler and I have bought a couple of pieces from him.
While not the top quality Reps they aren't all that bad for the most part in my experience. A few have been 'junk' so to speak but others have been quite good. My buddy is just getting into the rep watch thing and is testing this wholesaler for what he can/can't get from the factories.
I'm his guinea pig if you want to call it that because I'm so damn picky and don't mind telling him that what he has is crap, lol.
As an example he brought in a TAG Link Calibre S for about $50, wanted to resell for about $150 here in Canada.
Here's a quick and dirty wrist shot; (sorry for the small size), anyway....
It is an automatic and the TAG markings are good, but....No chrono pushers, running 1/10th and 1/100th dials, bad lume and the markers are poorly aligned just to name a few faults.
The ironic part, this watch arrived just as it was pictured on DHGate. So the only person to blame for it being a poor Rep is the uninformed buyer.