If I were to close this card I would reset the clock on getting a sign up bonus again. (youvebeenowned.org)
Considering you can only get the sign up bonus on each of these cards once, I'd recommend getting cards when they have increased sign up bonuses. (doctorofcredit.com)
Just keep in mind that by product changing you will not get the sign up bonus. (doctorofcredit.com)