I'm about to make tiny DVD backups, and I would choose Nero AAC for multichannel reencode.

I made some test encodes to test how far I could push the bitrate. I would go for LC also for compatibility if it wouldn't take too much bandwidth.

Using the quality parameter, the sound are not transparant to me (ABX'ed!) until i reach ~400kbit with q0.4, and at that point it's a joke to reencode it for saving space, since most AC3's are 448kbit.

Is AAC just not the right choice for multichannel audio files, or is Nero AAC not optimized for it? Are there a better AAC encoder for multichannel files?

Edit: Confusing misinformation

What did you use for reencoding?
Can you provide short sample (30sec)?

I just did a more extensive test than my previous one. Unfortunately, I was unable to recreate my 320kbit problem, so forget about that.

I've seen claims that AAC are AC3 superior, but in ABX testing i didn't reach transparancy until -q 0.4 (~400kbit - The source is AC3 448kbit).

A little sidequestion: Which AC3 encoder on the market are considered to have the best quality over bitrate?