im interested in a lowrance elite 5 or a gen2 5 model. im not sure what to buy i want a unit with sonar/chart plotter and down scanning imaging. im not sure if i need hdi or dsi i think hdi model is best but not sure. i really like the gen 2 but dont know is it has down scanning built in or if it is an add on nothing i read is perfectly clear on these matters and pricing them on ebay is confusing the same models may be $100. difference in price. im using the unit on a bass tracker mainly for crappie,bass and bream fishing. i have $650 for a budget and would like to get a unit that is expandable in the future. lowrance is preferred but not a must.