I think picking up a true NT is important. Think about it. With a 4 man front with 2 LB's and a nickel secondary, you are essentially playing with a 6 man front vrs potentially 7 offensive blockers. Regardless of the talent, the numbers just don't work out. By running a NT with you get an extra man to jam up the middle and it jams up the middle so we don't see the carnage in the middle we saw in Cleveland where the Browns could double team one DLman and STILL have even numbers on the rest.
That doesn't necessarily mean we should use it as our basic defensive alignment, but we SHOULD have the personnel that would give the option to do both.