Low gain preamp options

A passive might work with the amps I have now, but I've been looking at some others that have input impedances in the 10k range. When running at full volume that may be fine but at lower volume I think it might cause issues. If I remember right poor impedance matching can get you some roll off on the low end which is where you would theoretically want to boost it to compensate for perceived roll off at lower volumes. (Fletcher-Munson) 
The other thing is I really like whatever the tube in the Saga+ is doing. I think I'd miss that. When I first got it I did a lot of comparing to my MF A300 integrated preout even going so far as to use it as a pre into the A300. I'll need to start paying attention to how much I actually use the volume control. Maybe I'd like even more tube sound even if it means having to put up with only a very small portion of usable adjustment. I really hope the eventual solution isn't to spend $10k+ on a vinyl rig and record collection.

Aren’t variable or adjustable gain preamps just adding in another attenuator on the input? So yes, you do get more useful range on your volume control, but you’ve also knocked down your signal so you can then amplify it again. Maybe that’s the only way to get the circuit to do anything useful so your output impedance is regulated. There might be a minimum required gain to keep the circuit linear. That might be all a buffer does for all I know - attenuate the signal and then amplify it by the same amount for no net gain. Wasn’t planning on doing enough research on circuits for a DIY project. I was really hoping I just hadn’t found what I think should exist or someone could tell me a good reason why it doesn’t exist.

@verdantaudio it’s premature to start quoting custom equipment. I’m still trying to see what standard units are available.

@tablejockey the recent thread on the EVO400 volume control did give me some concern and prompted this thread. Previously I figured I’d be okay with anything under 12dB of gain, but I’m starting to have doubts, especially if I go with even more efficient speakers (>100dB).

Thanks for all the suggestions. I actually have looked into a lot of them. (I did make an effort to search before posting.) I’ll probably need to resign myself to some sort of compromise. Maybe 10-12dB isn’t too much. It seems like some of my desired features are mutually exclusive.

Because I want the option of using some low input impedance amplifiers, I don’t think a straight passive will be a good fit for me. I also like whatever tone a tube may impart and am interested in maybe getting a little more of that than the hybrid buffer of the Saga+ provides. I think a tube stage must provide more tone with gain though. This leaves adjustable gain preamps that seem to actually adjust the input attenuation rather than adjust the gain. (Still not sure on this.)

Maybe I’ll need to do more research on custom, DIY, and brush up on my electronics. If the actual gain of the tube circuit can be adjusted in conjunction with and opposite to input attenuation then there can be a neutral effect on total gain while listening for what combination gives the best tone or presence (or whatever magic it is that I like about tubes). Once that is adjusted a separate volume control and source selector could be added. I can’t be the first person to want something like this. Maybe it just isn’t worth the trouble.

Anyone recommend a good book on audio tube circuit design? The few EE classes I took years ago only covered the basics in solid state.

@georgehifi,
not sure where you're pulling 2k from. I have one amp now with 22k input impedance, and there are a some others that I'm interested in at 15k and 10k. I just don't believe in limiting my future options without reason. I also have the bad habit of leaving more than one amp connected to my pre even though I only have one amp powered at a time. Makes for an easier change, but it can present more of a challenge to a preamp. When I finally get around to experimenting with subs (that typically have class D amps) being able to handle multiple outputs simultaneously with a combined impedance under 10k might become more important. My arbitrary maximum of 500ohms would allow 10:1 ratio with two 10k loads in parallel. 

@wrm57 I missed that difference between the LTA MZ3 and the pre. Before the level 2 upgrade option I thought they were pretty much the same except for the tape loop and single chassis. The MZ3 (with 12AU7s to drop the gain a smidge) is one that I’ve been giving serious consideration. I need to take another look at the pre with the input specific gain control. I’m probably overthinking the gain issue, but I was short on things to obsess over this week.

@jaytor thanks for the link. I hadn’t heard of Hattor before, but it definitely warrants some serious investigation. A passive now with a tube buffer later if needed might keep my options open. I need to do additional critical listening comparing the passive to the buffer on the Saga+ to get a more specific idea what I like better about the tube.

@georgehifi it’s rare that I’m out pessimisted. Thank you.