[Elecraft] DSP question

[Vic Rosenthal]

I've had a  KDSP2 in my K2 for a few months now.  When operating CW 
(that's all I do) I find myself mostly keeping it set to LPASS with the 
NR on, and the decay parameter at 31.

Before I got the DSP, I tended to operate with the crystal filter set to 
to 400 or 250 Hz, mostly to improve the signal-to-noise ratio.  Now I 
mostly leave the crystal filter set to 800 Hz and let the DSP reduce the 
noise (alas, QRM from other CW stations is no longer the problem it used 
  to be).

I noticed that the NR does not seem to be as effective when the IF 
selectivity is high.  This makes sense, since the DSP has a harder time 
distinguishing between signal and noise when the noise is concentrated 
near the same frequency as the signal.

I haven't used the narrow DSP filters much, mostly because of an 
ergonomic problem:  the button seems to bounce a little, which often 
causes an attempt to change DSP filters to also change the crystal 
filter, driving me nuts.

My question is:  does the NR work as well with narrow DSP filters as 
with wide?  Or does the same effect occur as with the crystal filters, 
limiting the effectiveness of the NR when the bandwidth is narrowed?  My 
own listening tests have been inconclusive.

Vic K2VCO