You def shouldn’t exceed the rms power rating. That rating is basically how much the sub can take all day long without “cooking” the voice-coil. Power ratings are based on the thermal limits of the sub. The sub obviously also has mechanical limits but you’ll hear it when you reach those. I’d say look for a 2ch Class-D full range amp that’s 1ohm stereo/2ohm mono stable. You can start it on 4ohms mono with the single sub and wire it to 2ohms mono if you get another. Gives you future expandability and also gives you the option of using it for the front/rear stage if you buy a bigger sub amp in the future. There are some good options out there that’ll put out 400w @ 4ohms mono & 800w @ 2ohms mono. Ebay is the best place to look for ideas and check specs.