Bruce, I have a 420S and it works well. If the unit is complete with transducer and 2G map it is a good buy. I paid R9,500 last year for mine, but keep in mind that the 2G map alone cost R2,500 and if that is not included then the price is probably to steep by R1,000.
Without the map the R6,000 is to close to the price of a new one, then rather buy new.