I have owned two Kul ES-87 boards (one with clears, one with reds). Sold both, mainly because I prefer Topre or IBM buckling spring over any Cherry mx switch.
The Kul boards were reasonably solid. I particularly liked the abundance of options afforded by the DIP switches. The Kul has Cherry stabilizers, which make it easy to change keycaps on stabilized keys, but to me they feel mushy.
I have also owned a Filco MJ2 TLS Ninja with mx blues. Another very solid board. Sold it for the same reason: I don't like Cherry mx switches. It has Costar-type stabilizers, which can be tricky when changing caps, and they tend to rattle more than Cherry stabs, but I prefer the key action to that of Cherry stabs.
I also had a Poker II. Nice concept; I like the 60% form factor, but I sold it and got a HHKB Pro 2 -- a much better board all around. Apart from the HHKB Pro 2 comparison, I thought the Poker II was not of the same high quality as the Kul or the Filco.
One of my first boards was a Ducky Shine II with mx browns. I was disappointed with the quality and gave it away.
One of my preferred Cherry mx boards was a CM QFR Stealth with mx greens. Not bad for a Cherry mx board.
I also like the look and customization options of the WASD keyboards, but I have never owned one of these. They look to me to be on par with Kul, but with a few more features.
If for some reason I were unable to get Topre or IBM Model F buckling springs, and if I had to use a Cherry mx board, I would probably go for reds. I have tried mx blue, green, clear, brown, black, and red; of these, red worked best for me.