Just saying amplifier implies power amplifier only, too. There are various units that include amplification....2ch receivers, 2ch integrated amps, multich avrs (audio video receivers as mtrycrafts mentions), as well as power amps. The NSF51s are 6 ohm nominal, 89dB sensitive so any reasonable amp section should be able to drive them well. Need more information about other speakers, your listening levels, distance from speakers, etc.