What kind of PDFs? If they are largely text, the Kobo, Nook and Sony Pocket handle PDF the same - they reflow the text. reasonably well. If you're talking about graphic or image-heavy PDF, the Kindle DX or iPad are better options, although the Sony Touch has a zoom mode that can work in landscape mode. I'm not familiar with PDFs on a Kindle, but you'll have to convert any ePub to Mobi, which will require removing DRM for purchased books.
If you weren't happy with the Kobo's battery life, the Nook's will bother you, too. I get about 8-10 hours of reading out of my Nook - the LCD screen uses more battery power than a typical e-Ink device. So I just charge every 2-3 days.
Honestly, your price range is very limiting. Even the Kobo is more than $100. Just above your price range, I think your best bet is still the Kobo or a Sony Pocket, maybe consider the Sony Touch if you can handle the glare.
And there is always the used market - eBay, and is it Kiiji?