Have you tried
Isilo? I'll be honest and say I haven't tried Ubook or peanut on the PPC but Isilo certainly meets all the features I need.
It now supports memory cards (about time!), has font scaling, auto scrolling and a desktop component that can convert html etc to pdb standard.
I'm still waiting on my x50v so can't say how it rates on a vga display but they have a trial version on their website so I'd be interested in what you think if you give it a try.
Jel