What is AAX+/AACPLUS?

I have seen AAC+ being mentioned several times here and have looked in the wiki but haven't come to a coonclusive answer. Is AAC+ just a brand name for an AAC-encoder or is it 'AAC 2.0'?

AACPLUS is just a brand name for HE-AAC, which is an extension to the "usual" AAC codec. It's generally only useful for ~80kbps bitrate encodings maximum, most (all?) encoders don't allow you to select a higher bitrate.
HE-AAC encoded files can be played back by any AAC decoder, but the "magic part" is only decodable by special AAC decoders. The "magic part" is SBR, similar to what made mp3pro "good enough" at lower bitrates.
I know this all is not too technical, but someone with more proper knowledge will surely come along, if needed

The standard allows SBR at any target bit rate (Nero's encoder supports this), although using it at high bit rates tends to decrease transparency.

So is there some point of comparison between aac and aac+. aac+ at what bitrate produces a "transparent" sound?
Or is aac+ designed specifically for surround encoding and not faithful reproduction of two channel stereo?

The answer and a little more info here.

Regards,
Oki