The Hub has two 2.4GHz antennae and three 5GHz antennae.
The Link speed of a 20Mhz wide wireless N channel is 72Mbps.so as the Hub has two 2,4GHz antennae the maximum Link speed would be 2 x 72=144Mbps.
The Link Speed of a 40MHz wide wireless N channel is 150Mbps, so with two 2.4GHz antennae the maximum Link speed would be 2 x 150 = 300Mbps, so a link speed of 450Mbps on the 2.4GHz band is impossible with the Hub.
The Hub has three 5GHz antennae so the link speed would be 3 x 150 =450Mbps for a wireless N 40MHz wide channel providing you have a 3 x 3 wireless client.
The 40MHz channel is designed to automatically fall back to 20MHz if interference from neighbouring wireless networks or domestic gadgets is sensed. You cannot force a 40MHz channel width, which is usually a bad idea on the 2.4GHz band as said. The older Hubs did not enforce the fallback as rigidly as it is is now due to the 2.4GHz band getting even more congested and WiFi Alliance guidance.
I would bear in mind that the Link speed is the theoretical speed in one direction, ignoring overheads and actual speeds are about 50 - 65% of Link.
Acrylic reports that the max speed (link speed) of 2.4G is 144Mbps.... There is no other wifi in the area (I switch the othen APs off), no microwave oven, DECT phone etc, I never get two channels on 2.4G nowadays. Even 300Mbps would be good... And yes I have 2x2 2.4 clients