Credit Union/"Other Bank" advice

I've enjoyed reading a lot of the finance related threads on SD and now I am asking the gurus for advice/help...

I do not belong to any credit unions or banks that are not one of the major corporations. The research I've done seems to indicate that USAA and Alliant are two of the most attractive options and I'd like to see about establishing a relationship with one or both them. Is there a reason why it would be a disadvantage to use both organizations? (On another note, I know you don't have to be a member of the Armed Forces to use USAA banking services. Do you HAVE to be a service member to use Navy Federal? Because Navy Federal looks great too...)


Here are my specifics:

• -I am in my mid-20s and currently live in the NYC metro area
• -I would like to start this process with $5-10K, possibly increasing
  that amount down the line.
• -My checking accounts are usually active – debit card usage,
  writing checks, frequent ATM withdrawals, etc. I would be willing to
  adjust my habits for these accounts based on what would be the most
  advantageous.
• -Right now I only have one credit card (VISA, no annual fee) and I pay
  off the balance in full every month. It will be renewing in June, but
  I was also thinking about applying for an American Express with no
  annual fee. USAA currently offers this – does it seem like a good
  option and does anyone know if it is only a limited time offer?

Essentially I would like to know: what is the best way to keep this money accessible (i.e. liquid) while gaining interest and making some money? Combinations of checking, savings, etc. I don’t expect to make a ton based on the interest, but right now I have this money sitting in a “big bank” with a terrible rate and it is not doing anything for me.

Also willing to hear investment suggestions, but only "let it sit" investments.

Thanks for your time and suggestions!