Fico2Go, right now, your sig looks pretty nice, you can 3xCLI the Amex BCP in 61 days from your approval date and your sig will look even better. That you received an initial 10K on Discover is nothing to scoff about! 
Let your cards grow, and when you're ready, there will be a new round of card app posts on the forums. If you're going to garden for 6 months, you'll have a pretty good idea then if you want to ask for CLI's or go for a new app. Decide based on what is right for you, your spend habits, your own personal finances and your comfort level.
If your sig is current but relatively new, and if you app for a new card in 6 months, your credit history may be too short/ thin, unless you have other things in your file that aren't included in your sig. Be aware of that if you app in hopes of a high initial CL.