I've got a Strider Plus, costs a bit more than your $400 budget, but includes the toddler seat and all the accessories. Both seats have a shade canopy and the sun and rain covers cover both seats. Both seats recline so toddler can lay back for a sleep too. There is lots of space between the two seats too and you get some adapters to make the top seat sit slightly higher so there is even more space. The shopping basket is a good size and you can access it from the front and sides of the pram. It's easy to maneouvre and folds easily even with both seats attached. So far, I'm really happy with it.
One of the little problems I had with it was that I didnt think I could use the capsule on it (I really like our current travel system) with the toddler in the back cause there seemed to not be enough head height.

Do you know if the adaptors work with the capsule? I havent seen them anywhere, where did you see? Now my brain is ticking over about gettin the pram again.