Which Clie for ereader?

Hi (relative newbie) -- I've got a Palm TX that I use frequently for reading ebooks. I gave my sister a really old palm (M series?) that works - -but isn't backlit so she can't read at night.

I've never had a Clie and have read amazing reviews (even recent ones) -- and am considering buying my sister a used Clie (cheap would be good), but wondered if anyone could make a recommendation. I saw good marks for the PEG-TH55 (esp. battery life), but those seem hard to come by (and still expensive).

I'm a bit spoiled by the TX and it's expansion slot (I purchased a cheap add-on program that allows me to use 8GB SDHD cards -- maybe higher). I load lots of ebooks and videos and don't have to worry about storage space. It sounds like there are lots of Clie's that utilize memory sticks, but I've never used one and don't know their storage limitations. (Granted -- ebooks don't take up that much room...)

I'm a bit worried about buying a relatively old product -- my TX is having some serious touchscreen issues (I've purchased a replacement digitizer but haven't installed it yet); I wonder if Clies have similar age-related issues...

I'd appreciate your comments! For ereader purposes, I suppose I'm looking for backlighting, battery life, and storage. Thanks. mcaren