The Fisher X-100 series of integrated amps are very nice vintage pieces, but keep in mind that when it comes to equipment that is 50 years or so old condition is a huge variable. If the example you are considering has not been serviced in the last few years by a reputable professional, or by a knowledgeable hobbyist equipped with the right instruments and supplies (e.g., a Variac, tube tester, contact cleaner, etc.), I would advise caution.
Also, in choosing speakers for use with an amp such as that one you would want to avoid those having low efficiency, and those having impedance curves best suited to solid state (as opposed to tube) amplification. Many of today's speakers are designed with the expectation that they will be powered with solid state amplifiers. Feel free to post back for further advice on that when you reach the point of considering specific speakers.
Also, just out of curiosity, which model in the X-100 series is it (X-100 or X-100A or B or C)? Some of those models used very different tube types than were used in some of the others.
Good luck. Regards,
-- Al
