....the standard Harman Kardon radios are 2 ohm, but the CVO Harman Kardon system if 8 ohm standard and 4 ohm high output....
On the 09 SERG, you've got the standard radio at 2ohms, I'm pretty sure. No advanced autio system there. On the CUSE2-4, I think the audio system includes an amp. Maybe the amp is 4- or 8-ohm? I guess that could be the case, but I'm not sure why it would be set up that way. Also, I seem to remember that only one set of speakers (front? rear?) are powered by the amp. I might be confusing the HK Adv Audio system with one of the aftermarket systems here. In any case, if I'm not mistaken, the HK radio head unit is the same on all models.
These speakers should work fine on the SERG or any other bike with a 2-ohm system.
FWIW, mine came in last week. I think I'm going to head home and pull the front fairing since I've got HID lights, Kurakyn Driving Lights for Road Glide and J&M Audio Speakers to install. Could be a fun evening!
Oh, and I'm almost done with the break-in. Should have been weeks ago, but bad weather and being ill kept me off the bike for almost three weeks. Anyway, this means I'll be working on the exhaust -- non-CVO headers and Fullsac baflles -- and putting on my TTS Mastertune shortly.