Subwoofer or Bi-Amp?

Hello everyone. I was wondering which application makes more sense.

Should I buy a subwoofer or does bi-amping speakers effectively create a subwoofer situation.

It seems to me that using two separate amps, one for the midrange/highs and another for the lows creates a situation where you have a powered subwoofer without purchasing a dedicated subwoofer.

I hope that explanation makes sense. What are your thoughts? Thanks for your help.
While I can't comment on bi-amping, the subwoofer made a big deal of difference in my system. I have 4 large speakers, so called fullrange, but because of positioning in my living room and without room treatment at all, I was getting an abysmal bass response. I doubled the amplification power but I got only minimal improvements. by adding a subwoofer the sound is now just as I like it, well balanced. I don't think be-amping would have accomplished that in my room. But every room is different.
Any instrument including bass guitar produces much wider range than subwoofer can do. So without main speakers subwoofer alone will definitely sound dull.
In my opinion powered sub AND finely tuned crossover is better than bi-amping. Even better is to use two subs. But everything should be carefully tuned.
Hello again and thanks for all the replies. I also thought it might be of some help to inform everyone that my application would be a two channel music only system. Thanks again. All of the responses have been enlightening.

The lowest note on a bass guitar is an E, which resonates at 42 (actually 41.20) Hz, which is why you were able to hear it clearly, but not the subwoofer.