Slow Wireless Download Speeds with Actiontec mi424wr-rev i

Hello, 

I recently upgraded my wireless router from the Actiontec mi424wr rev e to the rev-i. My internet plan is 50/25 can get those speeds wired but wireless my  download speed barely get past 15mbps while my upload speeds exceeds 30mpbs. My pc is a Win7 and my wireless network adaptor is the D-link WDA-525. What could i do to get better download speeds wireless.

Thanks