I'm not sure what "new" means. I found a marketing cut sheet that was copyrighted 2003. In general I'm leery of units that have been sitting in a box for almost 20 years. You can have capacitor problems with these units too.

It's a judgement call. I'd open the existing unit and inspect it. If there are obviously heated areas, components in these areas could be primed for fail. In this case I might lean toward the "new" unit. Unless there are dozens and dozens of capacitors, I'd think about replacing the capacitors in the "new" unit. If you replace any power supply capacitors be sure to use a similar type of capacitor. In this area simply using the same value (at the best price, of course) may not yield good long term success.

Inspect the soldering, especially in the heated areas. Look for discolored glue areas. Some units used a light tan, almost white goop to mechanically stabilize things. Fast forward 10+ years and that goop becomes a medium to dark brown and it's conductive. I know some units that will spit and fuss until I scrape the goop from the PC board's input wiring. Listening to the unit, you'd imagine all sorts of really hard to track down issues, but one quick scrape with a knife fixes everything. Look for this goop near power supply capacitors. The conductive goop could inject noise to a nearby signal wire that is in the same pile of goop.