Surround sound via external sound card

[MobiusOne]

I'm looking to connect my W520 to a tv for watching movies. The video is all set up with a DP to HDMI adapter directly from the laptop to the tv. The sound, however, must pass through a receiver first. The receiver only has RCA inputs - it's quite old. I know the hypothetical setup would definitely work because I have a cable tv set top box connected that way.
What's missing is an external sound card that is:
- compatible with the w520

- capable of outputting 5.1 surround sound

- capable of connecting via RCA, be it through an adapter or not

Can anyone recommend a reliable external sound card for the job?

[Chatbox]

http://www.google.com.au/search?rlz=1C1LENP_enAU474AU474&sourceid=chrome&ie=UTF-8&q=surround+USB+dac

[lead_org Microsoft MVP Contributor]

i got this:

http://upload.wikimedia.org/wikipedia/commons/7/7f/USB_Soundcard_Soundblaster_Live.jpg

[MobiusOne]

Now that I've done a little more testing I have a more specific question. My receiver uses Dolby Prologic II, which means the front center channel is virtual and the rear channels are embedded in the usual two stereo channels.

I tried using a 3.5mm-to-RCA adapter before but it wouldn't even output stereo. Only the left channel was being sent to the front two speakers, nothing to the rear. 

Is this the fault of the adapter or the sound source? In theory, I don't need full blown digital 5.1 sound, so would I be better off buying an Intel WiDi adapter given that my ThinkPad is equipped with an Ultimate-N card and a Sandy Bridge i7, Or would that leave the rear speakers silent?

[alphaman]

I really wouldn't bother.

Just get a media streamer such as the WDTV Live. 

[Ldxrunner2015]

Greetings, Where did you get the referenced item ? Thank you.

[christopherlang]

Have you tried one of these?

dynadock PA3927U-1PRP dynadock U3.0

You can stream 5.1 audio (and the video for that matter as it supports two displays). It also supports USB3.0 as an added perk (the dock itself can be plugged into a usb 3.0 port for best performance). It has one HDMI connection, one DVI-I, and an ethernet connection builtin as well as the usb connections.

PS Missed the bit about you only having RCA connections on your receiver. Lol I would get a new receiver. But then again this device may help you as it does have analog outputs (front,rear and c/sub). You would need to build/find cables though (3.5mm x3 to RCAs).

Btw no SPDIF? If no your receiver must be a pretty old one. Hope its a good one ;-). If you have an coax/optical input then there are also USB devices that will provide 5.1 (maybe even 7.1 nowadays) via the SPDIF connection.