1.) Your computer can run Windows 7 x64.
2.) You can purchase a Windows 7 x64 upgrade DVD/license (at the reduced cost).
3.) You will need to perform a clean installation (wipe everything and start from scratch) since you cannot directly upgrade/convert from 32-bit to 64-bit operating systems (or vice versa).
4.) You will not need a BIOS update.
5.) Aside from being able to use more than 4GB of RAM, you likely will not notice much of a benefit unless those multimedia applications are available in 64-bit versions. 32-bit versions will work, but see little/no performance boost.
6.) Each copy of Windows 7 will include both 32-bit and 64-bit DVDs, so you can choose to 'convert' now or down the road.