I'm struggling to understand your hardware.
Do you have a home cinema already, or are you looking to buy one? All we know at the moment is that you've got a TV, TiVo, and PS3.
The Samsung you posted above only has one optical input and one coax input, which isn't ideal.
Its slightly over budget, but this is by far the best way to do it.
http://www.currys.co.uk/gbuk/pioneer...49154-pdt.html
It has 1x HDMI Out and 2x HDMI in. You connect your TiVO and PS3 to the two HDMI inputs (both devices are capable of outputting 5.1 over HDMI) and the HDMI from the Pioneer to the TV.
I would knock the DVD side of things on the head - the PS3 will do a much better job at upscaling than some of the home cinema upscalers.
Even something like this - although you'd have to supply your own speakers.
http://www.amazon.co.uk/ONKYO-TX-NR5.../ref=de_a_smtd
Hope this helps a bit?
If HDMI isn't your thing, then any device with two optical inputs will be sufficient.