Unless you need the money that's being charged for your annual fee (I didn't think there was a monthly maintnenance fee?) personally i'd just leave it open. Then again I fall into the minority of posters here who don't quibble about an AF: $35 or even $59 a year is trivial for a good tradeline... and a 5 year revolving tradeline with solid payment history is an *excellent* tradeline.
Cap One isn't a great lender, and you don't need the card with your scores and other cards now... if there's something you find fustruating about the card (like PIFing before the statement date, which I don't worry about except in the except when I'm trying to boost my FICO pre-application) then close it, but personally I wish I had your problem .
On Capital One Platinum they refer to what we call a annual fee as a "monthly maintence fee". I originally opened this line with no fee(s) but they decided to slide this on me a few years ago...they won't even PC me or reduce the fee...and yes i've tried the exec office a few times. Mine happens to be $5..which i believe is wayy too much because the card has no benefits. I only keep it open because it's been open 7 years with perfect history. Maybe once i buy a new car i'll close it.
If you close a card, the only immediate impact is on utilization (as the card continues to report). The OP said her utilization was 2% and this was among her smallest CL card, so closing it wouldn't increase utilization to bad levels. It makes no sense to continue to pay monthly fees for a card you don't use in that situation, your CR will still show the great payment record...