Charlie
With all those requirements, you would seriously be better off buying a cheap netbook (Asus eePC for example), unless you wish to splash out and buy a tablet like the iPad.
Some dedicated e-ink readers will play music but none play video as the display technology is not geared towards that sort of purpose. For video playback you will need a backlit colour LCD.
If you want to buy a dedicated ereader locally you have a goodly selection now. I would recommend the Kobo, Kindle3 or a Sony PRS-350. Neil does recommend the Kogan but I have heard there are many, many issues with it. But is is still worth a look all the same.
Another option is the Jetbook Lite. It is powered by 4 AA batteries.
http://www.ectaco.com/main.jsp?do=pr...fid=29532#spec
Stay right away from the cheap stuff offered at Officeworks, JB HiFi and DSE, These are cheap, yes, but you may regret the purchase. The three I mentioned above play nicely with ebook retailers webfronts and the Sony PRS-350 and Kobo ADE compliant.
If a netbook is a better option, then you can download ereading software such as Kindle for PC, Kobo Desktop, Sony Reader or Calibre which will allow you to read ebooks. The first three even allow you to buy ebooks online.
Anyway, these are naturally my opinions and may not sit well with you or others. Good luck and feel free to ask any questions. You are certainly in the right place to ask!