to pre or not to pre....that is the question....

I have Wadia 7/9 combo connecting directly to my power amplifier. Can I improve the performance by getting a dedicated pre-amplifier? Suggestions anyone...

Rest of the system:
Levinson 20.5
Sonus Faber Extrema

what volume level number is your typical listening level? If its 80 or above you are not losing any bits of Digital information. If below 80 the internal dip switches inside the Digital converter aren't set properly for your particular system and need adjusting. If level is below 80 typically a preamp may improve your sound but be sure your dip switches are correct for your system before considering a preamp because the Wadia volume control is very good when adjusted properly and not losing bits.
The improvement may not be that big but just different unless you are going to spend some cash. You would probably get more bang with a better CDP, ICs and cables, along with some tweeks. For example, the wadia 861 will probably sound much better than the 830 with a preamp.
Martin Colloms, reviewing Wadia 860 or 861 for Stereophile, said guardedly that he thought a very good active preamp was necessary for best performance. From my own experience with an Accuphase DP-75 and a CAT SLT Mk III with factory simplified signal path, I disagree--unless the active preamp is simply offering a partial filtering out of some nasties built into the Wadia, which I hasten to say I've never heard. Ask yourself: how could an active preamp help? It isn't the same issue as active versus passive preamp when the CD player must be plugged into one or the other, putting a third element into the impedance equation. (Maybe some wise person among us can answer my question, which I posed as a rhetorical one--but maybe it's not.)
This topic comes up quite often and the opinions seem to split about 50/50. I personally think it's better without, as I think the Wadias have a good output stage and can drive most amps quite well on their own. Others claim to hear improvements with preamps but I am suspicious that they are actually hearing euphonic colorations that the preamp is adding and like what they hear.
I agree with Karls. My only question is: do you need better volume control?
If you don't have to use a pre-amp then HELL no!