$16K is without the rebate and gets you a GDU 370 plus a GPS antenna, GDU 375 plus a GPS/XM antenna, ADAHRS, Magnetometer, OAT probe, and a 6-cyl engine sensor package .
The 430W point in irrelevant.
If you're going to fly IFR, you're going to pay that cost. It doesn't matter which EFIS you go with.