Just looking at the build quality, I would rate it higher than some of the other split dump/front pipes going around, maybe EVEN the trader you have mentioned!!!!
I recently purchased a stainless split dump in a GB and was less than impressed with the quality of the item I received.
The welds around the dump flange had been MIG'd from the inside and there was a nice 3-4mm bead of weld around both the exhaust and wastegate flanges, reducing the size of each by around 1/2".
I fitted it up in its delivered state, but it was eating away at me and I am getting my car tuned this week, so I ripped it off and got a die grinder onto the welds to smooth it all out, then got it welded from the outside (as it should have been in the first place).
Also, the flanges weren't stainless and they had been sprayed with some type of heatproof paint, very roughly, so there was overspray all over the pipe. The wategate separator had been attached so there was a gap between it and the flange, resulting in me having to file 5mm of the top of the separator to stop it fouling on the exhaust housing. Quality work!!
Pics attached