I have a $95 Profile Baja (including $30 shipping) amp with a rated 300 watts RMS and it sounds fine on my own subwoofer driver which is of comparable quality to the FI. The most important thing on a sub is motor control and decent headroom, so if the amp has a good damping factor and adequate power it is going to sound just fine. I doubt that anyone can hear the difference between 2% distortion and 0.05% distortion for subwoofer frequencies. On a sub there aren't going to be any high frequency harmonics in the output since the driver is totally incapable of producing them anyway.
So my answer is that you can probably even buy a cheaper amp than the ones you mentioned, as long as it has enough RMS output, and it will drive the most expensive sub driver just as well as an expensive amp. Human ears just can't hear the difference.
Good drivers are usually worth the extra cost, but the amp doesn't matter anywhere near as much, ESPECIALLY on subwoofers.
Even on high frequencies, if the distortion is of the right kind, our ears are quite tolerant of fairly high levels of distortion, which is why tube amps sound so good even with 1% THD ratings.
So my answer is that you can probably even buy a cheaper amp than the ones you mentioned, as long as it has enough RMS output, and it will drive the most expensive sub driver just as well as an expensive amp. Human ears just can't hear the difference.
Good drivers are usually worth the extra cost, but the amp doesn't matter anywhere near as much, ESPECIALLY on subwoofers.
Even on high frequencies, if the distortion is of the right kind, our ears are quite tolerant of fairly high levels of distortion, which is why tube amps sound so good even with 1% THD ratings.
