Thank you for the great comment pike!

The main reason for the 2.0 setup is space. My room is quiet small but I would love to get a full 5.1 setup. A centre channel really does wonders for multichannel tracks (I have had 5.1 setups previously, but using smaller speakers), but my current 2.0 setup does cope fine with multichannel tracks.
I do listen to a lot of CD's on my system, and it is nice just to have the two speakers, but if I do get to a 5.1 setup, I will again, just send the audio for 2.0 tracks to the L & R speakers. I am not a fan of matrixing i.e. Pro Logic II or DTS Neo:6 of which create a 5.1 sound field from a 2.0 source.