logitech 5500 or amp and speakers??

[frostman]

i have sky HD. I was using an amp(cambridge audio nothing special £80) and two speakers to get sound and it was pretty decent.
I know have a logitech z5500 spare sub and can run the same speakers from the sub. it is 5.1 but i only have to speakers so its not DD.

is my best option just the cambridge audio amp and speakers?
or the 2 speaker system with the logitech sub?

thanks