AAC compression rate question

Hi,

AAC has been quite an improvement to free up space while keeping decent compression quality (i.e. for headphone listening at least). Initially at 128kbps (near CD quality), the HE-AAC has in my experience enbaled to downsoze files more while keeping same impression of quality. I am now using 48kbps as standard importing/compressing rate since the HE has been intorduced more than a year ago.

Meanwhile, is this the latest advance in AAC technology? I am wondering if there are alternative to HE-AAC which at same quality are providing even smaller files, has like a lot of people, files get cramped on an iPhone or iPod nano wth only 16 GB!!!

What would your recommend as different rate or format to stay close to quality and create smaller files than HE-AAC, if this is possible?

thanks in advance for sharing experience

Y.