Advice on choosing a new mechanical keyboard.

Take a look at this, I have this Cooler Master CM Storm Trigger - $100 (cherry mx brown). its a great keyboard. I also play FPS games and I'm always typing on it, and it has been great so far

Personally, i'd suggest getting a separate wrist/palm rest since that would give you more options when it comes to choosing the keyboard. That can get expensive depending on the material and quality you want ($70 for a leather one from EK for example but if your material of choice is memory foam you can find those for under $20).

If you absolutely must get an included wrist rest then i'd suggest one of these depending on your switch of choice:

Blue (Give Feedback when pressed and make typewriter-like click sound)

Brown (Give Feedback when pressed)

Black (No Feedback, requires high force to press)

Red (No Feedback, requires low force to press)

For FPS gaming i'd argue Linear (Red/Black) vs Non-Linear (Blue/Brown) doesn't matter so much since you do some double tapping but not an insane amount like a RTS gamer would (arguably you can double tap a linear switch much faster because of the placement of the actuation and reset point so if you're doing hundreds of key-presses a minute the switch you're using can really make a difference).

Blue: Not a lot of options. If you want this switch i'd highly recommend the separate palm rest like above.

Brown: Logitech G710 - backlit, main con is it's arguably expensive ($170 - nearly double the price of many mechs, but still nothing compared to some of the top end ones).

Black: Steelseries 7G - no backlight, or a Mionix Zibal 60. Note both have fading key issues.

Red: Corsair K90 - backlit, has comfortable wrist rest. Main cons are it's not fully mechanical. Or the Gigabyte Aivia Osmium if you're willing to shell out a little more.

CM Storm trigger can be had in all switch types, just another one to consider. Personally I think the two best choices from the ones I mentioned are the Logitech and Gigabyte ones, so if your switch of choice is Brown or Red i'd go with one of those unless someone mentions a better choice.