If you have an ATU already with all the harnessing on one machine and AT ready in another and the 8430 I'd go Deere. Their steering of their own machines is the top dog for performance typically. Used stuff is very reasonable these days and all you'd need is a couple displays and receivers. If you're running things at the same time. Otherwise you can move displays and receivers around in about 30 seconds. 

The 8x30 isn't autotrac ready? Never heard of one that's not. What's the serial number?