[kwh1]

According to my a5+ manual, there is a rca output on the back of my speakers. Plug the rca cable to the output of my speakers and then hook it up to the input of the subwoofer.
 

 

[MrFahrenheit]

Yeah, the SVS is kinda expensive.. but it's one of the best musical subs for $500. Better stuff will cost you 900+ :/ so it's actually pretty good value hah and the way mine is connected is: Essence ST > RCA to SVS > RCA from SVS to Airmotiv. As long as you can do that, you don't need multi channel cards or an AVR. If the sub only has one digital out, it won't work :/
 
Also, I agree with the above posters, you should do a little research and perhaps buy from an ID OR wait for a good sale. HSU has some good entry level stuff for around 350 I think? Might be closer to 400 actually... SVS with its entry level at 500.
Look around, it's always better to spend a bit more time looking rather than jumping the gun too soon and then returning lol