I have this: MTX TC8001 Mono Subwoofer Amplifier, it does 800 rms @ 2ohms. I was used by my for about 2 months. That was 2 years ago. It's been in my closet ever since. 10/10 cosmetic and function.
I've got a Diamond Audio D3800.1 I'd sell to you for $125 shipped. It's in good shape and is rated at 600 RMS @ 2 and 800 RMS @ 1 ohm. I sold these for a while and they are strong amps.
Diamond Audio D3 800.1 (d38001) Mono Subwoofer Amps Car Amplifiers Car Audio Car Audio, Video, & GPS Navigation - Sonic Electronix