OH he's right. Most amps are rated 20-20,000hz, your speakers should cover the spectrum...
The finest most peak condition human ear can hear 20-20,000hz, 9 out of 10 human ears get only 40 or 50 to 16,000 or 17,000 of that range. As we age that gets worse, the average 60 year old man can't hear past 14,000hz but women have better hearing so they can hear stuff we can't, funny, they don't care about sound as much as men. If like me you cranked the volume alot and went to concerts then you have lost some range. Had a job in a factory or loud surroundings, sorry. A sub that goes to 25hz isn't going to miss anything that most of us could hear anyway. Anything below 20hz is not heard so much as it is felt and some subs advertise down to 18hz and even lower, imperceptible to anything but a machine or your poor dog.
Good things about the BIC F12 that sold me,
-decent power, both peak and RMS, see how I put the peak first, how misleading... BASH designed
-sheilded, important as it's close to my LCD.
-12" Hsu designed driver
-5 year everything warranty
-LFE and other connectivity options, numerous setting options as well.
What more could you want for $170, which btw retails here in Canada for about $450 which is more like $525US, and the guy has no stock, sells them like crazy.
Many people on this forum seem to feel that if you don't buy their brand of sub or you don't spend a certain amount you must be crazy. There are a ton of great subs out there, few at this price point but there are a few. After reading threads and forums, do your research by reading audio reviews and anything else you can get your eyes/hands on and make a smart decision for you and your system.
Good luck and good listening!