No it was pre-built, I can't remember where I got the box from, but I bought the sub separately.
I also disconnected the tweeters on top of the dashboard, I find them utterly no use nor ornament. On my MK1 Arosa, I took the dash tweeters out also, but there was enough space left in the hole to install a couple of decent 3" Sony speakers, which sounded great. However, on the Lupo/Mk2, there's barely enough room to fit your thumb in the empty tweeter sockets, so I've left them blank.