alarm - they'll cut the wire (cutting the wire by unprofessional thief will trigger the alarm)
lock - they'll break the lock
cctv - they'll wear a mask/cut the wire

If you listen to all comments like these, you'll go nowhere
so, use as many protection/deterrent as you can with the best quality you can afford..

lock : From my readings, yale is very good but very expensive..
alarm : It's good if you can afford to install alarm that comes with
monitoring service like ADT etc.
cctv : good for deterrent or for police investigation.
other options - security guard, dog