Will freezing affect the quality of a dry-aged steak? I'm used to buying moderately-priced meat from the supermarket, with which I can generally never tell the difference between fresh and frozen - it's maybe a little tougher after freezing but that's about it.

Today I happened to be in the area of a good butcher and decided to splurge on a couple of dry-aged ribeye steaks. The first one was, of course, delicious, but I may not have time for a home-cooked dinner during the next few days, so I'm considering freezing the other steak.

Will freezing do anything to ruin or diminish that unique dry-aged flavour and give it the same taste and texture as the supermarket fare? Since dry-aged steaks are already, well, dry, will the additional water loss from freezing turn it into inedible shoe-leather? Should I be worried about anything else?

Or can I just toss it in the freezer for a week?
Dry-aging primarily breaks down the connective tissues in the muscle, naturally tenderizing it.  The concentrated flavor is just a result of the moisture loss that you've already identified.

Neither of these should be affected by freezing in any special way.  You'll want to be especially careful about further moisture loss, but as long as you properly package your steak for freezing you should be fine.