The obvious choices for an inexpensive EInk reader in the US are the 5" Sony PRS-300 and the 5" Astak EZ Reader Pocket Pro. You can buy the Sony in lots of stores, and so try it out before you buy. The Astak is typicaly mail order, see
Here is the link: "A Christmas Carol Gift Pack" but it can also be bought on its own for $199 . Many ebooks you buy have DRM (encryption), and both these Readers support Adobe DRM (ePub or PDF). I like the Pocket Pro, but the PRS-300 is a good choice too.
The EZ Reader Basic may be the cheapest 6" EInk device, it is $239 with similar software to the Pocket Pro (but it is an older design, with a bit less capable hardware, e.g. USB 1.1 vs 2.0 and SD vs SDHC cards).
The Kindle 2 from Amazon is now a good deal at $259 (but you need a cover, which is extra). Don't be put off by the wireless, you don't have to use it and the Kindle is still tops in one-stop shopping. Amazon seems to have finally woken up to the fact that they need to improve their software over time to stay competitive. This is the safest choice of all, with hundreds of thousands of happy customers.
Many ebooks have DRM, but you can circumvent both Adobe DRM and the Kindle's AZW DRM. So your ebooks are not tied to your current device type.