You can get a small form factor 500 watt or greater power supply that will work with your 970. You don’t need a new card if it will physically fit in the case. As for a second hard drive, you can probably get a small form factor solid state drive and tuck it in somewhere even if there aren’t enough places to mount it in the case.
If you tell us what the model number is we can be more specific.
Better than a model number, I can give you the link to what I got.