Yeah, I'm really hoping someone offers carrier boards much like SparkFun did with their blocks[1] for the Intel Edison which passed the Hirose DF40 connector through to allow stacking.
For sure:
"Jetson TX1 draws as little as 1 watt of power or lower while idle, around 8-10 watts under typical CUDA load, and up to 15 watts TDP when the module is fully utilized, for example during gameplay and the most demanding vision routines."[1]
Anecdotally, the RPi2 has been measured[2] around 4-6 watts under load and the Edison was measured[3] around 1 watt.
Yet another: the 96Boards[1] DragonBoard 410c[2][3] from Qualcomm has a Snapdragon 410 quad-core Cortex-A53 with a good amount of connectivity and IO interfaces (as per the 96Boards spec) and an Adreno 306 GPU which supports the open source Freedreno[4] GPU drivers (if you have a binary blob allergy). That said, this thing has a whole different performance tier than the TX1, but if you wanted to start poking at 64-bit ARM, this thing might be worth a look, especially with the comparatively low price.
Could you provide some technical detail on the creation process? The Xbox One controller doesn't identify itself as a Human Input Device, so it requires a Kext, yeah? Did you need to use a USB sniffer to identify the initialization sequence and button mappings?
Quickly, you might take a look at the ODROID boards, they nicely cover the lower price and performance spectrum and do a nice job supporting them:
http://www.hardkernel.com/main/main.php
Relatedly, Mattt Thompson of Gowalla/Heroku/Panic/AFNetworking fame proposed Rocket, a technique that pairs JSON Patch and Server-Sent Events to aid in the construction of realtime apps via REST services. The proposal has seemingly been abandon, which is unfortunate as the formalization of handling was interesting, even if one implemented it on top of a different transport layer like Web Sockets or a push notification service.
[1] https://developer.nvidia.com/embedded/linux-tegra