Like you I used to read my off-line content with Avantgo. They are ridiculous with their 2MB limit! I tried lots of other things, like Hubdog, newsland, and several RSS readers. But most of them either did not allow you to subscribe to any webpage/feed you like, or it does not save the entire content off-line.
A good one I found to be pRSSreader (pda.jasnapaka.com), but it didn't work on some newspaper sites.
I currently use sunrise XP (
www.sunrisexp.com), a somewhat different concept. Sunrise XP is a desktop program that allows you to download content from any webpages incl. RSS, with options for linkdepth, filtering, images etc. It stores the output on your desktop (you might want to tell it to use your off-line folder for that) in PLUCKER format. Now you only need your plucker reader Vademecum (vade-mecum.sourceforge.net/) and off you go.
It has a very cool feature: in your desktop IE context menu it adds two options. One allows you to easily define a subscription from the current web-page, the other allows you to take a one-time snapshot of the page you are viewing. Very Very handy if you want to save e.g. an e-bay search result to your handheld, with pictures, contact details etc. etc.