Hello guys i need some help if u people can help.
I've swift 2013 dlx version. And it has stock alpine head unit
Which is showed in pic. (Its single RCA, with no subwoofer support, as far as i know)

I've installed a 4ch amp with 1pair of components infron and 1 pair of coax at back. Now i want to attach a sub as well. So please guys help can this unit support sub with compromising sound quality or should i upgrade headunit.
If i have to upgrade headunit then it must look like original theme of car. I've in mind that i should install swift navigation. Ref pic
This the screenshot from some website. I want to knw if this one is good for the setup, can it support a gud sub? From where i can buy this in karachi in cheap! Or anyother option you people suggest.
Thanks alot in advance.