Dell win 7 Slow wireless connection

Hello,
I have a fairly new Dell XPS 9100 PC. It Came with a DW1525 wireless N card installed. I'm having issues with download speeds. I went out and bought a new Linksys/Sisco E1500 Wireless N router and this didn't help at all.. All of my other devices work fine with the router, when I connect my phone it gets 25mb download speed and same with my tablet. I normally keep the wifi off on these items though. I've tried everything I can think of. Changed wireless channel. I even moved the router to 2 ft away from the PC. It has excellent signal but still 1mb download speed. One thing I noticed is when I set the router t0 (g) Mode only instead of mixed or N.. the speed jumps up to about 10-15 mb.. but when I switch back to mixed or N it crawls again.. I've been working on this for a week now and ready to pull my hair out. I even went to best buy and got a Netgear N600 USB Wireless N. and it does the same thing!! Same speeds, this makes no sense to me and makes me think that there is something in windows 7 or a setting in the computer and its not the DW1525 card as I had suspected. Im out of Ideas here, any help would be greatly appreciated.
Thanks!!!