Yes but.
You are speaking of "specific impulse", i.e., thrust per pound per second of mass ejected. NERVA/KIWI were capable of about 800-900 "seconds" (actually lbf-second/lbm) of specific impulse. Conventional rocket engines (chemical) cannot go much over 500 seconds.
BUT.
Solid-core nuclear engines have a very bad thrust-to-weight ratio. I believe NERVA was something like 8:1 or 10:1, certainly not as much as 20:1.
Thus nuclear engines are not a good fit for a booster; they are much too heavy and the launcher pays a heavy (sorry) price in payload. They are by nature space engines which must be launched on a high thrust and high-thrust-to-weight vehicle. By way of comparison, the Space Shuttle Main Engine (SSME) has a thrust-to-weight of about 60-70. Some of the small engines currently in use for missile defense have thrust-to-weights of hundreds or even a thousand.
--Boris