I have a 2013 Spark LS w/ 4 speed automatic
I replaced the stock front speakers with 4' Focal speakers that have angled/adjusting tweeters on them. I dont utilize the back speakers due to the 10" Rockford Fosgate Sub/Amp combo in the back. The system feels alive!!!
I took out the stock air intake (my god that thing is ridiculously restricting) and placed in a DC Sport Cold Air Intake. It accelerates nicely. An area for the MAF sensor is on the CAI to be able to be mounted onto it.
The stock exhaust is out and a 2" catback exhaust is in place with a magnaflow muffler. The car just roars now along with great inner-city acceleration. (Will try to have a compressed video of it soon)
Overall, I love the feel of the car. It's really unique. There is really so much that can be done to it to fully complete its sporty look.