Audio Track on x264.. how i can apply -xdb filter whitout loss quality ??

[DjDiabolik]

I have this audio track on a x264 file:

Audio
ID                                       : 2
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Codec ID                                 : 40
Duration                                 : 1h 24mn
Bit rate mode                            : Variable
Bit rate                                 : 165 Kbps
Maximum bit rate                         : 192 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 KHz
Compression mode                         : Lossy
Delay relative to video                  : 67ms
Stream size                              : 99.4 MiB (10%)

I need to apply to his a -3 or -6 or more -xdb filter because on my standalone this audio tracks it's reproduced like distorsion/disturbed.
I have try to use AviDemux but i obtain a bigger file size....... i have try Xvid4PSP but for AAC i don't know how i can set... because same things here i obtain bigger file size.

Can you help me ?