Using the older CD players isn't a problem to me at all. I've got a few (the NAD, a CD63SE, a Rotel '965 BX, and a Philips CD840) and I'm quite happy to use them while they still work. I'm finding that the NAD sounds a bit more natural than the CD63SE at present.
Regarding the loudness button, the way it works is as follows:
Set the main volume to the maximum level you want to use. Then use the loudness control to trim the volume downwards when you want to listen lower. This means that, in effect, you don't use the main volume control at all if you are utilising the loudness control. However, you can't use the loudness control AND the Pure Direct feature so you have to make a choice. Personally I can't hear a great difference with the Pure Direct, but the loudness control works very well. It doesn't boost the frequency extremes like conventional loudness controls. In fact you don't notice any overt boosting at all and yet it does sound fuller and more substantial at lower levels than if you turn the main volume control down. Basically it does a very good job of retaining the tonal characteristics of the higher volume level. Hope this makes sense!