Changed preamps. Seems like less power now?

It sounds as if your new preamp has lower voltage gain than your previous one. Yes, the preamp can affect the output of your power amp as it amplifies the signals from your front end so that it can be used to drive your power amp. There is nothing inherently wrong in using a higher volume control setting unless you start amplifying noise. If your preamp doesn't have enough gain, however, it could not drive your power amp to full power. Going to a higher-powered amp may not necessarily cure the problem. Going to a power amp with higher voltage gain, even though the ultimate power output may not be higher, is probably the solution you are looking for. If your disc player or phono preamp has variable gain you could increase the gain on these to account for the lower voltage gain of your preamp.

If I'm understanding your question....Don't know the specs of the PA's you mention but...it's likely an issue of higher gain (i.e. resulting in greater signal strength to the PA outputs) with your old PA. You SHOULD be able to attain the same volume, albeit, with the volume control closer to 100% with the new one as the old one... Some PA's (e.g. the Calypso) have a jumper that you can change gain (check your manual)...and affect volume control range. Generally speaking, if the (unclipped)volume that you attained before cannot be (mostly) attained with the new pre. there's probably something wrong with the PA(or one of your pres has a really exotic design/gain). Yes, absolutely, a speaker change will modify the volume but...that's a whole 'nother discussion.

Different preamps provide different amounts of gain. Some may provide only say 6 db. of gain, some as much as 26 db. or more. Depends on the design of the preamp. This variance definitely means there is some degree of component matching required. However, just because one preamp requires more rotation of the volume knob than another may mean nothing other than the taper of the volume control is diffferent. I believe your Anthem works in .5 db increments, so that may mean you've really got to rotate it if your your amp is of a lower gain design and/or your speakers are inefficent. When you crank it up, is it sufficiently loud for you? If it is, don't worry. It's generally worse to have a preamp with too much gain as your volume adjustment is imprecise and it may affect the signal to noise ratio adversely.

The previous preamp was very sensitive, but also would only be at say 10:00 O'clock position at a given loudness, while the other one has to go to 2:00. I am thinking that maybe I should match my components, and use an Anthem power amp. Wheather or not that will make a difference or not, I don't know.