I'll second the EZ-Guide+. Since the model has been eclipsed by the new EZ-Guide 500 the price has come down substantially. I've seen new ones advertised for around $1600. Even though it is WAAS based in the stock form I'll guarantee that it is capable of much better guidance than you are able to drive. I ran mine as a lightbar for a few days and then I bought the EZ-Steer and let that take over the driving duties.

One guy had a complete used EZ Guide+ and EZ-Steer listed here in the For Sale section for $3500 this spring. I think someone got a bargain on that package. Here is a shot of tillage guidance from this year. Field is nearly 1.5 miles long. WAAS drift was not an issue here as I worked the field "Skip-Pass". You really need to trust the guidance system when doing that. I wasn't disappointed.

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waas 1.jpg (64KB - 226 downloads)