Thanks to the advice of Alyks's comment, I've decided to officially take the plunge sooner rather than later. That's right - monolingual dictionary up in hur, bitches!
Considering I've spent about 30 minutes on these last four iKnow sentences, I can already tell that it's going to take quite some time getting used to. I expected that I'd have to look up definitions of definitions ad infinity; I expected that I'd barely be able to read these definitions. And I was right.
But even so, the value of being able to use my current Japanese knowledge to build upon itself is so incredibly profound. Yes, it may take me considerably more time to create a sentence card, but consider all the additional vocabulary I pick up along the way... not to mention, a more concise definition of the words I'm looking up, and working my reading muscles all the while.
I'm getting used to the various dictionaries at the moment - actually just realized that I've been using 大辞泉 (Yahoo's default, apparently) rather than 大辞林, the latter of which I'm finding is much more easy to use - not to mention, Daijirin has helpful example sentences and phrases, which I can definitely benefit from. Sweet.
All in all, I'm glad I took the plunge. It'll be a heck of a lot more work, yes... It'll most likely slow down my iKnow sentence progress considerably (at least for a while), sure... But the end result will be a greatly expanded vocabulary and the valuable skill of being able to use a J-J dictionary.