Actually, there *is* a way to do what the OP wants.
The Overdrive reader app for Android supports library audiobooks.
So if you don't mind reading on a 4" screen an Android phone can give access to both library text ebooks and audiobooks.
In the next few months, Overdrive wil be releasing their App for Windows, Macs, and iOS so at some point the iPod and iPad will also do the trick.
There is at least one Android-based color ereader (the Pocketbook IQ) that is open enough to allow installation of Android apps so, if you can get your hands on the Overdrive app, you'd be in business; it's a 7" LCD-based reader retailing for US$139.
If Overdrive gets their App onto the NookColor App store that would also be an option.