[anton]

Erman,
Welcome to the board. I would think seriously about something along the lines of a totemsub tahiti 120/130. It is very quiet and very accurate. For something like dentex you might want to PM shaneshac on this board as he hunts the med and dentex. I use both totemsub and riffe and for a very elusive fish requiring stealth and high levels of accurancy I would not select a riffe for this job.

As far as the Riffe goes, here is the info:
Model/stock/shaft and range hawaiian/shaft and range standard
C3/130cm/1 wrap, 2 bands, 9/32" single flopper, 4.11m
C3S/130cm/2 wraps, 3 bands, 5/16" double barb threaded shaft, to 6.11

Note that there is a lot of options. C3 models are C3, C3S and "C3XS" You can mix and match. The C3 will take 3 bands, 9/16 x 24" Shafts can be about any but common are the 9/32" x 57" hawaiian and 5/16" x 55" threaded double barb. The 3x "gun is 3 inches longer due to a 3" cocking stock for hip loading

Price wise I am not sure but you might want to look at a standard series model 3. This already comes with a 5/16 shaft, threaded w/ 2 barbs and 3 bands with stated effective range of 6.10m which appears to be what you want. You can add on a wing kit later and it accepts ALL riffe parts.

Hope this helps a bit-I would still go for the tahiti though.