I can tell you I could not hear any fan noise at all. They are silent. The build quality seems pretty good on the outside. They are light weight, which I love.
They seem to be an excellent choice to me. I got two XLS 2500 for my FA 18.0 subs (on order).
Specs look great.
XLS Drivecore™ Series
I think just one XLS 1500, which is 300wpc 8ohm, 525wpc 4ohm is more than enough.