What amount of money you thinking of spending? to be honest as Beta said it really is a low end budget system.
You would be better off saving your money and getting a seperate A/V receiver, blueray player and set of 5.1 speakers.
Have a look here http://www.richersounds.com/product/bookshelf-speakers/wharfedale/diamond-9.0/whar-9.0-blk and others at www.richersounds.com but please be aware they the system you have is never going to show how good the Wharfdale Diamonds are.
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