I don't own any. My collection was reduced down to just three DVDs (The Dalek Invasion of Earth, The Tomb of the Cybermen and Lost in Time) but they eventually were sold off, along with my older VHS collection (which was considerably larger and consisted of around 40 titles). I never watched them, even moreso after becoming a father. I ended up losing interest in the show and it wasn't until the recovery of the two missing episodes in December 2011 that my interest began to rise again.
If I were to begin collecting again I'd probably only go for a handful, namely the ones I sold plus The Beginning, The Chase, Inferno and a few others.