Well, receivers are expected to handle a volume level of 0 db. That's 'reference level' for an receiver using Audyssey so "cranking the volume to -10 dB" is hardly going to push the receiver.
As for the bottom end losing punch, a couple of things can be said:
- If you haven't listened to a system with the bass equalised before, it may well sound a little subdued compared to what you're used to but give it a few days before making up your mind and see what you think when you get used to the sound. We have a tendency to regard things which sound different as not as good as what sounds familiar to us and we need to take the time to become familiar with the new sound before making up our minds. After using the receiver for a few days, try switching Audyssey off to hear what things sound like without it and see what you think of the bass with Audyssey then..
- try turning the volume up to -10 dB of so and listen again. The ear is less sensitive to extreme high and low frequencies at low volume levels and its sensitivity increases as the volume level increases. That means that as you turn the volume up, the extreme low and high frequencies will seem to increase more than the midrange does so turning the volume up acts a little like a tone control in some ways. I said 0 dB was 'reference level' and DVD/BD soundtracks are actually engineered to be heard at that level in the listening position. You aren't going to hear the proper bass balance without turning the volume level up to that level, or somewhere close to it because of the ear's reduced sensitivity to those frequencies at low levels.
If you turn the sub level up you will do a couple of things which aren't good. You will change the balance of the bass content of all the channels on the disc which have content below a speaker crossover frequency being handled by the sub, and you will also change the balance of the disc's LFE channel relative to other channels. Depending on what sound is involved and what it's frequency is and where the crossover frequency is, that could result in some odd sounds. If you want more bass and you're listening at much lower levels than the 0 dB reference level, 2 better options would be to turn on 'night mode' or whatever the equivalent of that is on your receiver, or simply to use the bass tone control to turn the bass up a little. The best solution however, provided you can do it without running into problems with the neighbours or waking the kids or whatever, is simply to turn the volume up and get closer to the intended tonal balance of the soundtrack.
Turning all speaker levels up by the same amount isn't going to help because the balance between the sub and the speakers is going to stay the same and all you're likely to do is to play the disc at a slightly lower volume setting to keep the overall volume around the same. Provided the overall measured volume stays the same at the listening position, you really aren't working the receiver any less by raising the speaker levels equally than you would be if you leave the speaker levels where they are and just turn the volume up. The input signal from the disc is unchanged and the amp is producing the same overall volume level. The total level of gain through the receiver is the same and all you're doing is altering the gain in 2 different areas, the volume control and the speaker levels, by compensating amounts to produce the same overall result. Effectively you're "cranking the receiver up" by the same amount, to use your term, but hiding where you do it in the speaker level settings rather than doing it where you're going to see it in the overall volume setting.
Reasonable receivers, and I think any receiver with Audyssey correction qualifies as 'reasonable', are meant to be able to be played at the 0 dB level so setting the volume to -10 dB isn't going to push the receiver hard at all.