that aux adapter is an fm modulator. meaning it inputs through the antenna and plays through a FM station. not bad sound, but not the best either. a direct aux adapter would sound better.
i don't know if the steering wheel controls will work or not. you may need to modify the steering wheel for those to fit and if the headunit isn't compatable or you don't have the wiring for it through the car then it's a no go.
from what all you have mentioned i would just go with an aftermarket headunit. you can get one with aux, usb, bt built in. this will give you better sound quality than the factory with more options for about the same price.
2010 Volvo C70
2011 Harley FLHTK
Midwest Crew #22