Different chatbox

I know this is a popular subject, and I'm sure that it has been discussed before but when I searched for it there were just WAY too many results, most of which were useless.

I really like the forumotion chatbox, from its simplicity, to the fact that only members can sign in without separate logins. What I dislike are the [almost instant] auto-logoff, and that there are no sounds. If someone could suggest a chatbox that would meet my needs, it owuld be really appreciated.

My requirements for a chatbox are:
1. The script for it is not too long so I can post it in the Forum Description box. This way the chatbox is available on every forum page below the logo like this. If there's a different way of putting a chatbox on every single page, please share. I'm using phpbb3.
2. Only registered forum members can view and post. I understand that they would probably be need to make new accounts specific to the chatbox, but if it can be automated with the forum's login it would be awesome.
3. Sounds available for new messages, new login, logout, etc.
4. Fairly customizable with size, background, and colours to suite my forum.
5. Keeps a history of previous 500 or so posts.
6. Doesn't auto-logoff, or at least is longer than the forumotion's chatbox. I would want at least 30 minutes of no logoff.

I wish that forumotion would improve their current chatbox. It works great, but there is just not enough features in it. I understand that the auto-logoff is to save server space, but just a few minutes is far too little. And integrating sounds should be easy enough too.

Thanks in advance

suggestions from me are either Chatango or Mibbit. I am using Mibbit right now, but not on all pages. The code is pretty short though.