Explain 'matching ohms to me?

I am buying a pair of AKG 701 headphones,and am playing them thru my Rotel preamp. Somewhere I was told I had to match the ohms. I am totally illiterate in this ball park. I looked up the specs on the Rotel. Their useable headphome impedence is 8 - 2000 ohms. The headset is aroud 63 ohms. Can I run the head set thru the Rotel? Help me understand all of this? Thanks. Jack
8-200 means that they can run with headphones in that range. It is not the output impedance of the Rotel. So, is 63 in the range from 8-200?

The AKG is reported to be a pretty high quality pair of cans. The Rotel headphone jack is unlikely to be up to the task of showing you what they can do. Give a headphone amp a try, inserted into the tape loop of the pre. For detailed discussion of various hp amps, try head-fi.org.
Thanks, Swampwalker. I guess I'll have to wait and see. I had hoped to avoid the cost of an hp amp at this time. Jack1177