Yes , you will cut the HK's speaker wires( out) and run them into the amps high level input.
I dont own the Sound stream , but I have never bought a new amp that didn't come with all the pigtails needed for hook up.
Take your time and solder and heat shrink all wire connections and you'll be fine.
2010 FLTRX , Stage 1, 13" Madstad, Mono tubes, SuperShox, Heritage style bars. Alpine CDE-HD149BT,Soundstream Picasso Nano Series PN4.520 , 5X7 and 6.5 Infinity Kappa speakers
If I have to explain ,you wouldn't under stand anyway.