With the right valving, many of your higher-end shocks (King, Fox, Bilstein, etc) indeed can replace a dual-shock setup with a single shock.
I run single Fox 2.0s on the front of mine valved 30/90 (IIRC). I might change them to something around 40/90 should the opportunity arise, but overall I've been pretty happy with them (it's the rear shocks that are more in need of further tuning lol, they are 30/80 and it's too soft with the weight of all the camping stuff I'm usually carrying).
Dual (regular) shocks are generally fine for a TTB setup too however (should be a bit cheaper also). The shocks don't move at the same velocity as the wheel does, so the extra stiffness vs a single shock should be an asset. I've seen the tire rub against one of the shocks of many setups though, so be sure to check your clearances before you get too committed to it.