Three of the four new models use the new upscaling chip.
The HT-S7400, HT-S8400, and HT-S9400THX home theater systems from Onkyo have one thing that most home theater systems don't - the Marvell Qdeo 4K video processor. The inclusion of this processor means that if you end up with a 4K television before you pick up a new home theater system, you won't have to worry about upgrades.
These three models also include networking capabilities that let you grab music from internet sources like Pandora and Rhapsody or pull it directly from your home network. They offer a front panel USB port as well, meant for iPod and iPhone connectivity.
The high-end HT-S9400THX is - as if you couldn't guess - THX certified and comes with THX approved speakers. Both the 9400 and 8400 are 7.1 channel capable while the 7400 offers 5.1 channels.