Backup Solutions for my MacBook Pro+

I have a Macbook Pro (2010) w/500gb hard drive. I have one 500gb external hard drive that holds movies and my Aperture library. My current backup solution is a 2nd external hard drive (2TB) that I attach to my laptop while my smaller external hard drive is attached (it is not excluded from the backup).

I manually attach the laptop and 500gb ehd every week or so to backup to Time Machine

The problem? My laptop is approaching it's limit and I'm thinking that I need to move my iPhoto library off to an ehd as well.

I'm wondering if backing up to my Time Machine drive with a laptop and two ehd (each 500 gb) is smart or if I need to backup those hard drives to other ehd separately.

Also, I plan to buy an iMac for my family in the next couple of months. Not sure how that should impact my backup configuration.

I've also heard that in addition to Time Machine I might consider getting an ehd specifically with the purpose of being a bootable drive (via Super Duper)

With all of these options my head is swimming a bit.

Would love recommendations for a backup workflow/solution based on my equipment.

Thoughts?