Mulie,
For the 5760, the best bet is to use the OSD and enter setup mode> manual setup. This will only display via s-video or composite connection, the 5760 doesn't support OSD via the component level connections.
Under the speaker input option, one can use the remote's arrow selector to cycle to the subwoofer - the display looks like what you'd get for balance/fade in a basic car reciever - a line of hash marks that have "flat" somewhere near the middle. Not terribly user-friendly.
If weezz runs the YPAO auto-setup I virtually guarantee that it will set his subwoofer distance to farther than it actually is from his listening position, and the crossover to 120Hz or 160Hz.
Weezz,
I would set the sub volume to 1/2 on the sub itself, then run YPAO auto-setup. Then I would go into the manual setup, fix the sub distance and set the crossover to 120Hz. Given the rolloff you're likely to get from your main speakers, that crossover frequency is likely to give you the best (flattest) coverage in the mid-range between the mains and sub. You can always go in afterwards and adjust the crossover up and down to see if a different setting subjectively appeals to you more. An SPL meter reading will confirm the best objective setting.
After that, you can play some music or movie scene you are familiar with (make sure the movie is Dolby Digital 5.1 or DTS 5.1 at least, and play it in "straight" mode), and if you need more low-end, let the sub's internal amplifier do the work by turning it up slightly. If it (the sub) is too loud, turn the level down in the receiver to make sure you're making the most efficient use of the receiver's power.
Lastly, you can try the "bass boost" to see if it provides some improvement, really as a last option to achieve enough volume from the sub.
Good luck !
Cheers,
Matty K