Hi, Acoustat and all other electrostatic speakers I know of should be plugged in all of the time. They take a while to sound their best after being unplugged.
I am not familiar with your HK amplifier, but I know electrostatic speakers are hard on amplifiers and very few solid state amplifiers sound good with electrostatic speakers. Your least expensive solution will be a used Acoustat TNT 200. This is a 200 watt per channel amplifier designed for driving Acoustat speakers.
Acoustat 1+1 did not come with a subwoofer and in my opinion does not need a subwoofer when powered by an appropriate amplifier. The 1+1 should have plenty of bass on its own. The Model 1 came with a subwoofer.
I am not familiar with your HK amplifier, but I know electrostatic speakers are hard on amplifiers and very few solid state amplifiers sound good with electrostatic speakers. Your least expensive solution will be a used Acoustat TNT 200. This is a 200 watt per channel amplifier designed for driving Acoustat speakers.
Acoustat 1+1 did not come with a subwoofer and in my opinion does not need a subwoofer when powered by an appropriate amplifier. The 1+1 should have plenty of bass on its own. The Model 1 came with a subwoofer.