Why go with active preamp?

First: if you think you can use the CD players volume control.... well??? are you an audiophile? That CD volume control ahhhh... Hmmmmm (sucks)
Hmmm ahhh . oops, no second reason.
But really, try it, if YOU like it, why not?

In my experience, an active preamp offers more flexibility and better dynamics to the music. Running passive can sometimes rob the music of its "liveness."

If a player only has one set of outputs with variable output, adding additional gain stages will only amplify what the player is already passing through its' built in attenuator.

On top of that, so long as the player already has more than enough output and is capable of easily driving the amplifier to full output and beyond, one should not run into the typical "lack of dynamics" situation that many people feel occurs when running passive or direct.

In addition to all of the above, Cdc mentions that the cdp being used has a buffer stage built in, so the player itself should be less sensitive to cable changes, etc... Adding another gain stage that is sensitive to cable / impedance changes could easily reduce the sound quality that such a design is capable of providing.

For the record, i typically prefer active preamplification for multiple reasons. BUT, and that is a BIG "but", if everything is accounted for with a well designed cd player and it is your only source, i see no reason why this should not work out quite well.

As mentioned above, try it and see. Personally, i would want my cd player to be capable of producing at least 3 - 4 volts on a steady state if i were going to do something like this. Running a player with lower output levels may get you into trouble. Obviously, this is an amplifier dependent situation so there is quite a bit of lee-way involved. Sean
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I've got an Adcom GFP-750 so it's easy to compare passive vs. active. With a good CDP with output buffer, I don't see much difference in dynamics. I think the CDP output power supplies may also affect dynamics but maybe someone with more experience would know better?
With a cheaper CDP which did not have the output buffer, there was a fairly noticeable loss in life to the music. Even though it has 2 volt output.
But I think a goldpt or DACT passive attenuator may give better transparency than the Adcom. The Adcom seems to lack ultimate transparency. At least that's what people here have said going from Adcom GFP-750 to a Pass Aleph preamp. The other option I have is to upgrade the volume or capacitors on the Adcom.
I don't see how anything could be more transparent than a DACT attenuator. But if there is an impedance problem, maybe an active pre is necessary. I've read some passive pre's have a resistor network to correct for these potential problems.
Some passive pre's are very expensive. Look at Placette ($1,500) or FT Audio's Little Wonder ($600). That sounds like a lot of money for a volume knob in a box. Does anyone have experience with either of these?

So the main question I have is: other than dynamics, is the purpose of an active preamp to be a tone control to further tweak the sound of the system?

Sean nailed it. I have played around with many passives (transformer-coupled and regular resistive, etc.), and none of them did EVERYTHING right as opposed to the active linestages I have used. Even with most actives, something has to give, but the best I have heard are the Audion preamps from the UK- basically a buffered line stage, point-to-point silver wired simple circuit using 3 6922's for the phono stage and one for the line stage. The Premier Quattro 4-box version (dual outboard power supplies) is da bomb...