I have history with their bigger brother the L520. Bought a pair brand new in 1980 and still have them. They are still in near mint condition and I just can't seem to part with them. I use them in a secondary system and drive them with a NAD 326BEE amp. I would think the L420's are similar, just won't go down as low.
The L series are reasonably high in sensitivity at 92 db but are low in impedance at 6 Ohms nominal, 4 Ohms minimum. They are also acoustic suspension speakers so they do like power. A 4 Ohm stable amp is recommended. Overall, I still think they sound awesome after all these years and I absolutely love the metal grills. You can see the drivers through them. Kind of alleviates the argument of grills on or off.
Good luck!
The L series are reasonably high in sensitivity at 92 db but are low in impedance at 6 Ohms nominal, 4 Ohms minimum. They are also acoustic suspension speakers so they do like power. A 4 Ohm stable amp is recommended. Overall, I still think they sound awesome after all these years and I absolutely love the metal grills. You can see the drivers through them. Kind of alleviates the argument of grills on or off.
Good luck!