In a moment of weakness, I ordered the new Kayhan Audio setup AND the G8 Designs kit with a Pioneer W8400NEX headunit. I haven't installed either, but have opened both and have some thoughts. I didn't take many pics of the G8 Designs kit, so most of this will be about the Kayhan.
The Kayhan comes attractively packaged in a hard cardboard box with magnetic closure, with purpose cut foam to secure things in place. So good so far. The trim around the unit is sturdy with what seems like a durable finish. The G8 Designs trim, by comparison, is a thin shell with a finish that seems like it'll be easy to muck up. Mine came with some handling scratches that are sizable, but only visible under certain lighting angles, so I might not notice them much if at all when in the car. And people seem happy with the kit, so it'll probably be fine. I've talked to the guy and he says if it's a problem, he'll make it right. The Kayhan didn't have any of that. Kayhan's install instructions are absent from the kit. The guy with the Facebook account says they were making a Youtube video showing the process. LOL, as I'm typing that sentence, he IMs me a link to the install. Talk about timing! It's 42 minutes long. I'll have to watch it later. G8 designs emails a lengthy and well detailed PDF instruction set. I haven't attempted either install yet, but it seems like the Kayhan will be a little easier, requiring less splicing. G8 Designs requires a few splices that Kayhan manages to build into the harness. It's probably mostly unavoidable because the G8 Designs kit is designed to use with any number of different headunits, so that's fine. One of those in the canbus connection, which seems like it could be in the main harness connector like Kayhan does, but would need a whole large section of open pin sockets for just one wire. So G8 Designs included the splice, along with all the rest of the splices you'll need, to save a little money. That's only a nitpick, nothing major. The Kayhan's wiring is all well labeled. There are one or two that I'm not sure what they are. I'm sure it'll be in the install video. G8 Designs' is all well outlined in the install PDF.
Some pics. Sorry some are sideways. Tinypic rotated my vertical pics and I'm not sure how to change it back.
Some of the G8 Designs kit. Mostly the marks on the trim.
There's a scratch here that is pretty much invisible under indirect lighting.
Visible under direct light.