The numbers you are seeing is the amount of channels a receiver can handle

The first number (normally 5 or 7) is for 5 channel surround (2 fronts, 2 surround and a centre speaker) or 7 channel surround (2 fronts, 2 surrounds, 2 rears, and a centre) 

The second number (normally 1 or in expensive receivers 2) is the amount of subwoofers that can be handled by the receiver.

If you are looking to power only 2 speakers you can pick up a 2 channel receiver. Examples below.

http://www.futureshop.ca/en-CA/category/stereo-receivers/10573.aspx?path=efc014fcb15aeb4ce5cfb518b8b...

Alot of 7 channel recievers will also be a muti--zone reciever. This will allow you to setup a couple of speakers in another room of the house (or a patio) and be able to listen to different sources on each zone.

EX: You are in the living room watching your favorite movie in 5.1 surround, and the wife and her friends are on the patio listening to the radio or CD's at the same time.

 P.S. Harmon Kardon makes a good reciever

One thing to take into consideration is that 95% of the movies out there are still only in 5.1..not too much has been released in 7.1.  7 channels better than 5 though.. I have a DennonAVR888 7.1  amp  very happy with it