Well it depends on what type of aerator that you want...if you want the stand on, well those are expensive. But you should be able to pick up a fairly inexpensive one, it will probably be a walk behind but you'll make your money back quick. I bought one last fall and before the fall was over I made my money back plus more.
On the dethatcher, do you have a zero turn? If so get a JRCO mounter dethatcher for your zero turn. The walk behind dehatchers almost pull up too much thatch, I only use those for very bad lawns.