I put 200 for 1770s, because that's where I've tested them on the Dyno on/off and know they're not a massive restriction.
The 4040s are definitely superior in flow as Steel mentions, but they're quite a bit more expensive. They are overkill for the rocket, but that just means flow will be good. The internal shape is far superior, but at what power level that starts to matter... No idea.
Ramair is more than enough for any N/A bike that's not modified internally, it's convenient, it puts the IAT sensor in the flow of intake air, and fits under the claw easily. Foam is superior to cotton for flow once it gets even slightly dirty, and the dirtier the filter the more the flow gap between foam and cotton, favoring foam. Foam also doesn't force the air to make a 90 degree turn as it passes through the media.
Cons: Foam requires a little bit more care to ensure it doesn't dry and become brittle, meaning, oil that filter!
Not sure why one would use the 1680s, the underclaw K&Ns, with Ramair on the market to be honest, unless you already own them.