Newbie - Blaster Live platinum 5.1 output

Sorry if this seems very simple to the experts out there. I want to get 5.1
sound out of the above card. What speakers will I need? DoI need a
decoder? Which output would I use?
Thanks
Graham

Sorry if this seems very simple to the experts out there. I want to get
5.1
sound out of the above card. What speakers will I need?

I'd say 5.1 speakers, preferably. Of at least decent quality, but most
such systems selling with an included decoder are of decent quality anyway.
(My personal recommendation: Logitech Z-680. One word: awesome.)

DoI need a decoder?

Yes, for the Live series you do, as these cards can't output 5.1 analog.
Also, 5.1 output will only work with previously encoded material (read: DVD
movies), when using the digital output. The only computer sound solution so
far that can output realtime-encoded 5.1 audio is the Nvidia NForce chipset,
so games etc will not be in 5.1 audio with a Live soundcard. There you have
to fall back to the standard 4-channel analog outputs.

Which output would I use?

The spdif plug (likely of the coaxial type), though it could be optical
TOSLink too. You'll find appropriate cables in a hifi store.