The new ones have internal GPS antenna. So if wanting to be really accurate for marking way points ducer would have to be mounted right by unit. Some of them new units come with a compact ducer that is different than the one on 998. If buying new and you get the compact they have a program where you can exchange it for regular SI/DI if you don't open package. If you want to have GPS at the transducer you can buy a external antenna and hook it to the new units. From what I have been seeing pretty new 998's are going around 1000.00. You can go to Bassboatcentral and check their electronics board for sale. Always plenty of units for sale. Also from what I have been reading they made some changes in the processors on new units to improve SI/DI it affected the quality of 2d side of unit, not a good thing if you use the regular 2d a lot.
Proud Member of Team Geezer
Charlie Weaver USN/ENC 1965-1979