I'm afraid you are not going to like this but i think you will need a new home theatre set up to get the best out of the ps3.
Looking at the specs of that model i don't see how you could connect the PS3 other than by scart. It does not appear to have either component in or HDMI in.
Also the only option to connect the ps3 to it for audio would be analogue stereo connections.
This means you would have about the worst sound and picture combination going via the home theatre.
If you don't want to replace the HT system you could always connect the ps3 to the TV directly for picture and connect it to the analogue stereo inputs to at least give sound through all the speakers but you would not get proper surround sound that way. If the tv only has 1 hdmi in you would also need an hdmi switch.
All in all i would just explain that now that your wife has conceeded the need to get a ps3 she has to also conceed the need to hear/see it at it's best - and that means a new HT set up.
Good luck in selling that to her
