So heres an off topic question for you guys....

I used to use SPDIF for audio out on my computer. With the optical cable and the whole bit, there was no volume option on the computer end... just on the speakers end. The volume option on the computer was fixed somehow and wouldnt allow adjustment.

Well, I got a new computer that doesnt have SPDIF out and now there are two volume adjustments. The computer volume, and the speaker volume.

Whats the best setting of both volumes for best sound quality? 50% and 50%, or what? I know that at some point, the volume control on the computer is just a distortion of the signal as its boosted and sound quality drops, but at what point?

PS. Computer is a MacBook and speakers are Logitech Z-5500.