A surge protector is a good idea to have. It was recommended to me to get one with both over and under protection as low voltage can do just as much, if not more damage than a surge.
This thread was very helpful to me in deciding what to get. I ended up with the surge guard 34750 for my new 5er. The portable units like the one I got are cheaper but are at a higher risk of theft than a hardwired unit.