what they wrote me is:
" même sur ses entrées RCA, la fréquence de coupure haute du CUB 3 n'est pas réglable mais fixe ; à cet effet son usage reste réservé au Home-cinéma ."
which translates to:
"Even on the RCA inputs, high-cut frequency isn't customizable but fixed. For this reason, its usage is really limited to Home Cinema".
Of course, if I can't parametrize the high-level frequency filter I can't have the sub seamlessly "merge" with the fronts, which is why he's suggesting to look at another model/brand.
So basically it's a classic low-pass filter, just with no configuration it's no good for high-level inputs and in general for music configurations.
In my personal opinion the Cub 3 might actually work if your amplifier has a good audio processor and can correctly configure the LFE out (my HC Anthem is actually very good in 2.1 audio too)
I did a quick search for Rythmik and Unluckily I couldn't find them here (France) definitely not in the shop I use that has almost every brand you can find in the country... and where I'm hoping to get a replacement!
For the price, and with high-level ins, I can get an Elipson (French) or a Tangent (Danish).