I got the Fishhawk X-4 last year and I have never had a problem with it. It is a big improvment from the old 840. The Probe works awsome with alot less blow back than the old unit. I have used the other units on different boats and the bigest problem I see with thoughs units is the coated cable. It seems to always get nicked and you start to lose signal. I would recomend the X-4 to anyone even though it costs a little more I think it is worth it.