Well.. as a one and only developer of PsyTEL AAC encoder I could give some hints..
at the early stages of development we all thought it was impossible to 'match' FhG AAC quality

However, latest versions of PsyTEL AAC are very close to FhG at 128 and 96 kbps bit rates, and even better for some VBR presets.
FhG still has edge at 32 kHz / 64 kbps, and lower bit rates because AACEnc is not tuned completely for these bitrates yet, but this is being carried out right now
I think that using of LiquidAudio has very little advantages, except if you are encoding at ultra low bitrates. First of all, this is a 'ware' software, it is not adhering the ISO standard (it has proprietary wrapper) and it is not possible to play files on other OSes.