How long have you had your Cap One card? They gave me a couple thousand more after I had them for a couple of years.
Also - when you call them, they base their limit on your history with them, they don't pull your CRs. When I called, they told me I was approved for $500 or something - I said "oh is that it?" Then they got more info from me and gave me the larger increase.
That's my biggest credit card limit and we've got about the same scores. Let me know if you get anything bigger!