People will tell you that the KBD67 Lite is the best-value for the money, and they will be right.
KBD67 Lite comes with a polycarb plate [be sure to pick that option, at least], hotswap [or soldered option?], an interesting retro-style coiled cable, RGB lighting, choice of case colour, and it's gasket-mount or something instead of tray mount. Even the stock stabilizers are decent, and sometimes pre-lubed. You can retrofit PCB-mount stabilizers to it, which you should do.
My experience is that it offers a better typing experience than $100+ factory keyboards. The case design and polycarbonate plate allow a thocky sound, which is highly desired, and the polycarb plate improves the typing characteristics of tactiles and linears. The KBD67 Lite tends to drop in a big drop every once in a while, so make sure to get on the list [maybe there's some available now?]
Another popular contender is the IKKI68 Aurora, which used to go for $110 in Round 1, but it now $135 for the base model. It is a different layout than the KBD67 Lite. The KBD67 uses a 65% layout with a blocker for the arrow keys, which is nice, but overall it's not identical to an ANSI / ISO keyboard. The Aurora, by contrast, is basically a stripped-down TKL that removes one column from the nav cluster and the F-row, but is otherwise very close to a standard ANSI configuration. Like the Varmilo VA68. It's up to you which you prefer.
Aside from the layout difference between the KBD67 Lite and the Aurora, the Aurora comes with more dampening material. Honestly, the KBD67 Lite is the best for undampened sound. It's very thocky, and people like it. But if you are dampening, the Aurora comes with the appropriate materials, and you can more easily make it quieter than the KBD67 Lite. It's probably easier to customize the sound of the Aurora, if you're into that. The KBD67 Lite is better out-of-the-box, and doesn't necessarily require any assembly.
The base-model Aurora is $135, but if you want the Bluetooth PCB or any other exotic PCB, it's probably closer to $200. Round 1 also offered a brass weight for only $35 or so, and it turned out to be exquisitely detailed.
Both of these models are popular. The base Aurora sold for $110 in R1, but retails for $200 or more in the aftermarket. The Aurora with accessories retails for $300 in the aftermarket. KBD67 Lite are also sold in aftermarket for well over retail price. So in a way these are $300 keyboards, if you didn't get one in GB.
If you want a metal case, those options are available for KBD67 Lite and maybe Aurora, or you can just get a normal KBD67 MK2, if it is available. These will be more expensive, and closer to the $300 mark at retail.
I personally would have a hard time justifying paying more than a retail KBD67 Lite or Aurora, since they offer such a great experience at that price. I don't know what a $350 kit brings to the table that is justifiable, other than metal and fancier corners. Keep in mind though that there have been some problems with PCB production for the Aurora, so you could get a damaged PCB. Haven't heard of too many problems with the KBD67 Lite. But all of these things are being manufactured quickly to meet demand.
