To get enjoy 'HD sounds" using your PS3 you need the following:
1. BD that offers either Dolby Tru HD, DTS-HD or DTS-HD MA.
2. Use HDMI connection instead of the optical digital out.
3. Make sure your firmware is resonably up to date otherwise it may not be able to decode DTS-HD MA.
4a. In the Cross media bar, go to settings and select video settings.
4b. In video settings, select BD/DVD Audio Output Format (HDMI), select Linear PCM, DO NOT select Bitstream because only the PS3 slim model can bitstream HD codecs. The older model such as yours must decode them internally and then output the HD signal in LPCM to the receiver.
If you have done everything right, when playing a BD that offers say Dolby TruHD 7.1 if you press the select button on your remote controller you will see the display on the upper right corner that shows your are in fact listening in Dolby TruHD 7.1 Ch.
There are quite a few PS3 users around here so if you need more help just let us know. You can also try reading the manual, may be ask your wife to read it if she can't stand the non HD sound.
Actually I find even the non HD sound very good so I wonder if you might have messed up some of the settings in your receiver, or may be you need to upgrade your speakers. The Klipsch speakers you have are not bad but the 5308 is a very high quality receiver so I think it deserves better speakers.