There will be some bigger screen devices announced in the next couple of weeks. Including the Plastic Logic Que. Best to wait and see what comes out as short answer is that there isn't really anything good on the market now for a reasonable price.
The Irex 1000 does an ok job, but is $1000. The Kindle DX displays PDFs fine, but lacks key features--at least for me--like table of contents, stylus annotation etc.
This thread has a recent discussion on the topic as well.
https://www.mobileread.com/forums/showthread.php?t=66554