Good/bad idea? Oppo in 2 channel w/out preamp?

Yes, I have used the Oppo volume control (whether driving an amp or a preamp is not relevant). The only issues are the the gain of the amp and the sensitivity of the speakers. The Oppo VC was just fine in the upper range from about 75 and up. Below 50, the sound was increasingly grainy. In between, it was tricky, generally OK and depended on the program content.

So, if all you need is a bit of attenuation, it is OK. How much do you need?

Sandstone-my amps are VAS Audio Citation Sound II which are Cayin's upper end (upper end for Cayin anyway) EL34 monoblocks based on Harmon Kardon's originals. See the ToneAudio online review to get an idea of quality of these amps. 12au7's are Amperex Globe Logo and 12ax7's are GE blackplate 5751's. EL34's and 5ar4's are Shuguang (for now). The input impedance is 47k ohms.

Kal-my speakers are Legacy Focus clones using Eton drivers though I have the woofers disconnected in favor of dedicated subs. I'd estimate sensitivity in the low-mid 90's and I don't have info on the amps' gain.
I must disagree with you as to whether driving an amp or preamp is relevant with regards to my question/situation. It is the point of my inquiry. I won't be making this purchase of a modded Oppo presently if the Oppo's volume control isn't sonically up to driving my amps. As mentioned in the body of post, I've used a player w/vc that really needed another volume control in front of it to sound in control while a couple of others were clearly NOT in need of such. If the Oppo volume control compromises the sound, I'll keep my Upgrade Co Denon 3910 for now and have a suitable passive built.
And please forgive my ignorance but what do you mean by the upper range from about 75 and up and below 50? Sorry to be a fool and thanks for your input!

Kal-as to how much attenuation I need-as much you would need if this was your sole volume control (as it will be I go with one of these Oppos)

I used an Oppo without a preamp and found it to be generally good. A slight loss of lower frequency weight and dynamics. Less "full" in the mid range (vocals). A bit of soundstage flattening. I thought the top end was excellent and all frequencies were very transparent and "fast." Unless you buy a very good preamp ($2K+ used), and assuming that the amp matching (sensitivity) is satisfactory, going direct is a good thing. My experience is that a "lesser" quality preamp never improves sound. So IMHO, unless you want to spend some dough on a good preamp, going direct to the amp can be a good thing (and assuming that this is the only input).

Lcherepkai-

It is not that the VC is good or bad. It is simply that it is a digital attenuator and, as such, must lose resolution with attenuation. Almost all do. (There are some that get around this by DSP.)

So, a little attenuation means a little loss and that is usually OK. A lot of attenuation means a lot of loss but it may not be an issue if the listening level is very low.

So, again, it is a question of how much attenuation you need and I cannot estimate this for you as it requires knowledge of your speaker's sensitivity, the gain of the power amp and what listening levels you use.

The numbers refer to the Oppo's volume indicator scale which ranges from 0 to 100 but is uncalibrated.

Kal