Why does bi-amping speakers sound better?

Thanks for the input/options everyone... it has helped however I still can't decide :)

i am actually leaning towrds trying a class d amp from d sonic.  Debating mono block, stereo or multi channel.  I did visit a local audio shop yesterday, they mentioned they had a NAD 5 channel class D amp at $4k, Anthem 5 channel A/B at $5k and a McIntosh 7 channel A/B at $6,500.  I mentioned/asked about multi channel vs stereo/monoblock and his response was since I use a AVR (Integra DHC 80.3) that I wouldn't see any benefit from mono blocks or a 2 channel amp.  If I didn't use a AVR then yes monoblock or 2 Chanel amp is much better.  

I am leaning towards trying class D due to moving into a old home, built 1865 thus not the best electrically in the place.  I worry that if I go with and amp that's A/B that it wouldn't get the juice it needs.  One of these days when money is willing I will run 1-2 20A service to where the stereo stuff is but that's going to be a while.  

Yes, my 8.1's are rated around 300w, however for a really long time I have been one who likes having more power then less power.  I prefer my ears say no well before the amp or speakers say that's to loud! For whatever the reason I have always thought it just sounds better that way feeding more power.  I also hope to get a better old infinity speaker at some point.  Possibly just the kappa 9.1's or their renaissance 80/90 or preferably something from the IRS line.  Thus trying to think ahead so whatever I buy now will have enough oomph to power whatever I get next... which will be a few years down the road. 

Good point on redoing the wiring first.  However if I don't buy a amp I can't listen to my stereo. 

Its a old building as as I stated, 1865 is when it was built.  It's actually a apartment above one of my funeral homes, taking advantage of free/no rent for a while.  I believe I have a fuse panel upstairs in the attic so it probably will not be that difficult to rewire.  Paint, carpet then I need to find  out where the stereo sounds best before I run new power lines to a wall.  

This thread has been informative!!!  Thanks again everyone for their $.02 :)  I am still leaning towards bi amping these speakers, just need to figure out how much power to go with.  

i went up into the attic to look at the power panel, I was curious how easy it will be to bring a 20a or two service into my front room and also my bedroom.  It looks like I have several opening to run more power, I counted eight available slots so I should be good.

i also do not think it will be to difficult to run the new power wires into the rooms, being a old house they aren't the standard 2x4 construction but 18+ inches of brick, rocks etc.  Thus the power cables will not go through the wall but on the wall where I can see it in the room, that's how the present wiring is (has a aluminum covering).  I think the access from attic to room shouldn't be to bad.  

Well...  being a old house I needed some plumbing work done,  toilet swap, faucets, garbage disposal and shower controls.... I was worried a little job would become big if I did it myself.  Long story short it did still become a major job, found several leaking fitting behind drywall in not so easy places which resulted tiles are falling off around the PINK bathtub...l thus my buy amp now money is need a shower/redo bathroom money,