Okay will try to help you out mate...
1) Put GT5P Sound Settings To Smallest Room Setting
(I found on my system it gives more bass)
I have mine on "small" right now, but there is option for Living room. Not sure if this is smaller or not.
2)If you can set your AV LFE to +10 or MAX output and lower the speaker volume to -5. The test with a higher volume level.
I have my AV LFE to +12 (max). What I didnt do was lower the others.
3) 100Hz Crossover should be fine
(The higer hte more it will rumble with standard noises like wind etc)
I got something right
4) Read the manual regards the high/low filters
If your talking about the manual for the receiver/amp I got about as good of luck finding that as a needle in a hay stack. Have moved twice since I bought either one.LOL
It will take time to get this tweaked for your own system and preference.
Take a note of the settings you like and for that game, sometiimes you may find you want different settings for different games.