Youghinyou can do it, someone can correct me if I am wrong, Inserting a picture that will help you. You might run into some volume related issues, as you will need to set the volume independently on both units.
Youghinno problem buddy, this is what I would do - If you own both units
1. Take your Sprout 2, connect it to your PC via USB
2. Buy RCA to 3.5mm splitter
3. attach the RCA portion of your splitter to your Sprout 2 Analog RCA out
4. attach the 3.5mm portion of your splitter to Sprout 1 3.5mm in
5. Now you have audio source going to both amps
6. Take Sprout 2, and hook it to your Left/Right speaker Woofers (I am assuming your speakers support bi-amping. This method will only work if your speakers can bi-amp)
7. Take Sprout 1, and hook it to Left/Right Tweeter
Enjoy your music!