Technically, most stock Subaru intakes are "cold air intakes".
As for any performance upgrades via intake and exhaust... well, for the 4th generation Impreza the best I could find was this...
STI's Japan-only catalog:
http://www.sti.jp/parts/catalogue/impreza_gjgp/index.html
The parts listed on the Japanese site do apply to the same exact chassis designation (GP, indicates Impreza 5-door hatch), however certain things will not fit due to the differences between the XV and the regular Impreza.
In summary, the sole power-related bolt-on upgrade available in Japan only is the STI exhaust. Though historically, exhaust upgrades for Subaru's soft off-roaders requires a different mounting setup from the non-lifted Subaru vehicles.
In general, stock Subaru intake systems do a decent job of keeping water out of the air intake. As for exhaust, I would simply have a reputable shop make a custom-exhaust suited to your local area's laws and your personal tastes (aesthetics and/or performance).
Usually the turbocharged Subaru vehicles get much more attention from the performance aftermarket.
The non-turbocharged Subaru vehicles can often be found without any available upgrades, so the best you can do is do a custom-job on everything you want to do. We're probably not going to get much from the aftermarket for performance parts.
What I'm hoping for from the aftermarket aren't necessarily power upgrades, but a clutch upgrade. A higher-torque clutch with a clutch plate that has a higher heat resistance would perform better for off-road use.
Honestly, some of my upgrades for my future XV when I do get it and then drive it past the warranty period (regarding power and drivetrain) would be:
* upgrade clutch
* head port and polish
* custom camshafts
* custom engine management with custom tune
* high-flow air filter (NOT an oil type! DRY type)
* custom retrofit STI or Bosal muffler (axleback)
Sadly, it's extremely expensive to get any kind of extra horsepower or torque out of a naturally-aspirated Subaru engine, especially considering it's not a very big market at all.