Meridian M Series
I owned a pair of Meridian M20 speakers for several years. The only significant issue to pay attention to when choosing a preamp is gain. Like most UK gear of the period, the amps have input sensitivity of about 0.5v. If you match that with a Brit or Euro preamp like a Meridian 101 or a Quad 44 with output voltage intended to drive an amp of that sensitivity, easy. But many American and Japanese preamps have more gain and are designed assuming the power amp input sensitivity will be about 1.5v - 2.0v to drive to full power. Without a master level control, and depending on the volume pot taper, you may not have much useful rotation range on the volume control of a high-gain preamp.
I used my M20s with a NYAL NCP-2 6dj8 preamp which was a modest 12 db gain. Today, lots of preamps fall in that gain range whereas in the 1980s when full preamps were more common and line stages were just emerging as common items, 18db - 25db gain preamps for lower-sensitivity power amps were more common.
Phil