Digital BW, The Print

Can someone please explain something to me - I've either set up
incorrectly or I'm failing to understand something. This is, I
believe, a more general black and white question even though I have
also posted on the QTR group:

I have my Epson 1290 set up with QTR and am happy with the standard
paper profiles for the time being. I've printed out a couple of images
using the curves. I wasn't using any soft proofing - just looking at
the curves and the resulting images. So when I did decide to set up
the proofing profile in Photoshop, I used the supplied QTR grayscale
profile and also enabled two switches: 'Preserve numbers' and
'simulate black ink'.

It is this last step that has me a little baffled. With the black ink
simulation enabled, the monitor does indeed very closely resemble the
printed image. But this image seems to have 'muted' deep blacks - it
looks like a kind of compression in the very dark tones. If I uncheck
the  ink simulation in the proofing profile, of course I can see more
'depth' to the blacks. However, since the point of the profile is to
simluate the output, I leave it checked.

However, if I take the same image in Photoshop and use Paul Roark's
curves, and the grey gamma space for soft proofing, I get these same
deep blacks both shown on the soft proofing as well as getting a much
richer output. I'm not talking here about the differences between matt
and pearl or gloss paper - I'm curious to know why I cannot produce as
deep blacks with the RIP as I can with Photoshop curves. I don't like
not having any proofing available on screen so don't want to use the
curves workflow if I can help it.

Is there something I've missed or misunderstood?