Make sure you look at the Fish Hawk and Smart Troll. I've heard blow back on the sub-trolls gets pretty bad when you go deep. Calumet Marine has the best price on the Fish Hawk X4D. Great service too. The Smart Troll doesn't have the speed working yet, but it tells you the depth of your lure. The probes are $175 and can be run at the rigger or on your line. So if you know a certain amount of Cu runs 50 ft deep at 2.5 mph and your probe says you're at 40 ft, you know you are running a little faster that 2.5 mph. If your lure is at 60 ft, you're running a little slow. Darrell from Smart Troll says he hopes the speed issue will be worked out mid-summer but probes purchased now will be good for reporting speed once the issue is worked out. Also, the website mentions interference is caused when trolling above 800 rpm. Darrell said that issue has been resolved.