BTW: I think iPhoto 5 and PS Elements 3 is a powerful tandem for most digital photographers, and all for less than $150. And I think the Pentax cameras are terrific :)
That being said, your desires are more advanced than many iPhoto users would seek. I wish there was a great answer for you, but I haven't found it yet.
I would be tempted to open my RAW files in Elements 3, make the adjustments in Camera RAW, save out as a Photoshop file, then catalog in iPhoto 5.
Not pretty, but you've saved your adjustments in a non-destructive format and can still enjoy all of the other benefits of iPhoto.
Let's hear other ideas about this from readers... There might be a better solution.