Stock NXT bolt works pretty well, actually. Better than the stock SFT bolt, in any case. Would be better with a spring mod or an aftermarket springed bolt, but i digress. Much smoother, yes, main advantage to any spoolie. But like most spoolies, maintenance isn't a picnic. Sooo many o-rings! But i love spoolies. However, I'd want to pay less for a used NXT. $250 at most.
For that matter, i'd expect to pay less for the Etek2, about same price range. Etek2 really benefits from a Zick kit (hammer upgrade), which would be my personal requirement for getting that (either knowing it currently has it, or knowing someplace i can get it - current Zick kit won't fit the older eteks).