Linksys Wireless Router :: E2000 Max Wireless-n Speed 72 Mbps?

I just bought a refurbished E2000 wireless-n router with 1 Gb LAN ports (from Cisco online).This router is meant to replace my Netgear wireless-n router that only have 100 Mb LAN ports.I have 10 devices in my home network, 6 of them are using wireless (1 'g' and 5 'n') and 4 are interconnected with cat5e cables (trough the router).The devices have some different operating systems and their network adapters are from different brands.When I set up the Netgear router I didn't have to adjust anything for the wireless network to work fine.All wireless-n devices worked at 150 Mbps (sometimes going down shortly to 130 Mbps).The wireless-g device worked at 54 Mbps.For the last 2 days I've been trying to set up the E2000 to achieve a wireless-n speed higher then 72 Mpbs... without success.I tried all the suggestions that I found in the Cisco Knowledge Base.

- Upgrading the firmware to the latest version

- Trying different channels and channel widths

- Different wireless security methods and many others.

Also trying different settings on the different devices doesn't work.Changing the distance between router and devices as well as changing the location of the router don't affect the results.Switching on only 1 device at a time doesn't change anything either.It looks like the E2000 is set to not transmit on a higher speed than 72 Mbps, when it's actually supposed to achieve a wireless-n speed of up to 300 Mbps. I would be lucky if I get the half of it, but not if it's only one fourth.