Micca: That's what I've been sorta doing. Both my K701 and DT990 has a somewhat similar volume level (the K701 is at about 10 o clock, and the DT990/600 at around 11 at the most). I set it pretty much for 11 o clock the Logitech speakers and set it to the general volume volume I like to hear it with the Logitech's volume control... =/ I don't really like the K701 for music, so I only use it for gaming which has a whole different level when I use my Mixamp as a pre-amp anyway.
Feiao, my speakers aren't really anything special, as it's only used when I get tired of having headphones on my head or away from my computer chair.It only has a 3.5mm plug. So I should max my speaker's volume control to max and use the E9 to control volume....okay I'll do that. I don't mind adjusting the volume between the headphones and speakers anyway. I'll just make sure to lower the volume when I unplug the headphone's and use my speakers.
edit: At speaker's maxed volume, my E9 is at 10 o clock, which isn't bad considering my main headphones are at 11. Sorta wish the 990s were a litle easier to drive so the volume on the E9 wouldn't change, lol.
I know for headphone's the source and pre-amps should be relatively maxed in volume, and the device the headphone's are connected directly to should be the one adjusting the volume. So it's different with my budget speakers...