Amex 3x CLI coming up and wanting to up my AAOA

[shifter]

Hey guys, 
Long time lurker, first time poster.

Just yesterday, I applied for the Discover IT and Capital One Quicksilver card. 

I was instantly approved for both, The Cap1 card gave me a limit of 10,000 while the Discover IT card is 3,000 I believe from the way some questions were worded about limits.

My question is, I have an American Express BCE card that I signed up for in January of last year, and I was an authorized user of a friend's Amex back in 2006.

I was hoping just to apply for another Amex just to increase my AAOA, not even sure which one I would get.  I don't really want any a card with fees.  

The other thing is I'll be up for a 3x CLI in a month or two, my limit right now is 7,000.  I originally had a 3500 limit, but didn't do a CLI unti 6 months.  

My credit karma score is 738 right now.  When I first applied to Amex last year, my score was 788, probably to do with the AU from a friend's amex and my Chase +1 I had since 2008, that converted to a freedom.  PIF every month.

I would like to get the 21,000 limit and then get another amex to really help the AAOA of the two new cards I just qualifed for.  Mainly I want to set myself up to be able to qualify for a great within a few years to buy a house!

Here is my AAOA currently:

Average Account Age	7Yrs5Mos
Oldest Open Account	8 Yrs 9 Mos
Newest Open Account	4 Yrs 1 M

With a total of 4 accounts, before the 2 new added additions

Any suggestions guys and girls?  Thank you!

[Creditaddict]

You should put in the CLI first and then follow that up with the app for a new card.

[shifter]

I thought so, but I also realized if I did get another card in January it would backdate to this month, I wish I would have requestioned that first CLI before July!

Oh well, I guess that's what I might consider doing.  Would it be likely they would allow me to apply for a new card and get more credit ontop of the CLI or would I have to transfer a bit?