I've purchased my headunit (A single DIN Sony DSX210X) and small digital amp (Alpine KTP-445U), but nothing's installed yet. I didn't get the Bluetooth version, as I prefer to load up a USB stick and leave it in the stereo, so it's independent.
I now know I don't have space behind my seats for a sub and I'm waiting to get speakers until I'm further along. I'll definitely get component speakers with tweeters in the dash and woofers down in the kickpanels.