Connecting YSP-600?

Hello was wondering if anybody can help me set up this as the sound is slightly underwhelming at the moment.

So I have a Samsung BD550 37 TV (which has an optical out)

PS3 ( which I use as my Blu-Ray)

YSP-600

Second part of the question I think I would like to buy a Sub but only have about a £250 budget. Happy to look at second hand and wondering what you would recommend?

Thank You