Ferrite Cores for Power cords

I am new to DIY and just made two power cords based on the Oyaide Tunami cable and Furutech connectors I purchased from vhaudio. My understanding is that I can possibly enhance the performance of these power cords by fixing ferrite core cylinders/boxes onto these cords. I will highly appreciate your advice/comments on the following regarding ferrite cores :

- Where can I buy them and which are the good ones/brands ? Any online source for buying these will be great.
- Should I attach them to both ends of power cords or only one end is enough ?
- Is there anything else I should know when I use them to derive maximum performance from the power cords ?
- Is it normal to attach the ferrite cores on interconnects and speaker cables as well

Please share your experiences.

Thanks in advance.