Based on my experience, having additional accuracy won't help you when you're driving by hand.  The display and our reactions aren't fast enough to make the adjustments needed to take advantage of the accuracy.  I started with a simple light bar (Teejet Centerline 220) and it was loads better than foam markers.  Now, I still drive the sprayer by hand, but I have automatic boom shutoffs and mapping and I would hate to go back.  I can't help you on what the best choice might be but I think if you keep an eye out for systems on marketplace or other classified sites, you'll be able to go much cheaper.  I ran across an EZguide 500 last year that I bought for $100, system, receiver, and harness.  It's a lot more capable system than what you linked...

Mike