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You don't need a new CC, you just need to increase the CL on the current card that you have. Might be difficult in today's climate when banks are routinely slahsing people's CL. But that's a bargaining point, call up BofA and say that you want to increase you CL but you're wondering if you should get Cap1 card or get another $500 of Credit on your current card... ask for a manual review, too, before they go ahead and do that computer review (which you have a higher propensity of failing).
I'd continue to PIF and ask for the CLI early next month, right after your pay off the card.
If you have a CC and a store card and you PIF, then increasing your CL isn't going to affect your score, because your util will be the same.
However, I would let about 1% report on one card. This might give you a small increase.
Having those two cards already, I wouldn't apply for any others until you are done shining up your report.
Those who go from no revolving to adding revolving or no CC to adding a CC, usually see an increase due to "mix of credit".
You say you really need to apply.....for what reason? If for your score, I doubt you see an increase, possibly a decrease due to the new inq/new account and lowering of AAoA.
Since you are asking about secured vs nonsecured, I don't think you mean you need the available credit for use, right?
I would read Credit Scoring 101.