If I were you (but I am not
), and if I am using the Euros 8 (is it the complete package including the sub?), I will do the following:
all channels set to large. I learned this just recently when my brother showed the effect it has in the surround channels including the fronts - it attenuates part of the midrange spectrum that all channels can handle, removing a portion of the body of sounds emanating from the surround channels. Let the surround speakers roll off the lows naturally. The only cons for the front is a possible difficulty of positioning them without it sounding boomy in the bass. This is why sometimes it make more sense that the fronts take only about 50hz and above freq to avoid placement difficulty arising from bass freq if a subwoofer will be employed anyway.
The subwoofer should be experimented on varied position. As subwoofer is an animal that communicates too well with your listening environment, listening experience will depend on the optimum positioning - from muddy, boomy, to tight and tonally balanced with surrounds. The following are factors that can be varied, and may take time - probably not just one sitting - and with correct test materials.
(1) positioning - corner loaded, away from walls, facing any wall, at the back of a couch, etc, etc
(2) adjust cross-over in the sub - since euros8 fronts are LF capable to a certain degree. Thus, try to tune the subw where the euros front cuts the LF (probably at 40Hz or below). At this setting, you might notice that you will not be able to hear the sub anymore since the euros fronts will take the usual bass freq from 40Hz up. But you might hear the euros subw at freq passages below 40 hz if the euros subw can handle it. having the front and the sub take up 100hz/90hz which yamaha sub out cross-over can only result in a further boomy/messy/bad bass reproduction - that putting off your subwoofer maybe the best sonic you can hear out of the euros.
(3) if there is phase adjust in euros8, also play and experiment with it.
