Re-take the GMAT if and only if you are extremely confident that you can score much higher on the quant section (i.e. the quant score you got was a "bad hair day"). Otherwise, I would focus on the written applications. The 64% isn't good, but it's not totally fatal given your academic background - it's not something that every individual adcom would overlook, but some of them would overlook it and give you the green light if the rest of your application is strong - that's why I think you need to be judicious about retaking the GMAT.
Also, if you want to go into marketing/branding, go for Kellogg over Columbia.
Alex Chu
alex@mbaapply.com
www.mbaapply.com
http://mbaapply.blogspot.com