Ass it happens Home cinema is my kind of passion.
To get the most you will need Bluray for the true 7.1 HD audio as you probably know. You will need to go for the separates option as all in one 7.1 systems are massivly overpriced and pish !
As mentioned above the PS3 is a good startpoint for the Bluray as it does have the HDMI for Picture and Optical out for the sound and the PC Media steaming is a great feature is you use the Ethernet conections via Router (wireless can sometimes be a bit laggy)
Moving onto sound, Apmlifier. Now I swear by Yamaha. You can buy any issue of What Hi-Fi magazine and they always come out tops and I can vouch for that as I had an amazing Yamaha set up a few years ago however they can be pricey.
You want to be looking for somthing like any of
these and If you do have a Richer Sounds near you it's well worth a visit as most of the time the will set a demo up with the items you want to buy.
If in doubt What Hi-Fi mag will set you right.
Good Luck
P.S. when you do get sorted, Transformers 2 1080p with 7.1 TureHD will blow you fucking sock off !!!!!