The introductory level system is the Zephyr, also called the DCS50. This is a relatively new system and is an "all-in-one set" with the throttle perched on top of the command station/booster. You can expand the set with walk-around or radio throttles such as the DT100, the DT300, or the DT400. Some of the features of the Zephyr is that the power supply is built into the system, you can read back the CVs (configuration values). It has an output of about 2.5 amps and you can run up to 11 trains at once on your layout.
The Empire Builder is the second-level DCC system produced by Digitrax. The command station/ booster that comes with this set is the DB150. Depending on when the system was produced, it may come with a DT100, a DT300, or a DT400 throttle. You can program the CVs in a decoder, but you can't read back the CV values as you can with the Zephyr. This usually doesn't stop your enjoyment of the system. It has an output of 5 amps and you can run 22 trains at once on your layout. You can always upgrade your the DB150 to a DCS100 if you find a DCS100 at a good price on the used market.
Digitrax discontinued the production of the DT100 throttle when it introduced the DT300 throttle about 4-5 years ago. It then discontinued the production of the DT300 with the introduction of the DT400 throttle about 2-3 years ago. Both the DT100 and DT300 are excellent throttles, still work extremely well, and can be picked up at good prices. Some people still prefer the older DT100 and DT300 for it's compactness and ease of use (the DT400 has a large number of buttons on the keypad).
The only difference between the set that you are looking at and a new set is the throttle. The used set has a DT100 throttle. A new set would have the DT400 throttle. If the price is right, you probably have a good value.
The next level up in Digitrax DCC sets is the Chief. The command station/ booster is the DCS100. This is the super-daddy of the 3 systems. You can run up to 122 trains at once. It produces 5 amps of power. This amperage is more than sufficient for any home layout.
As with the laundry soap manufacturer's, Digitrax is now prefixing the word "Super" in front of their sets (eg "Super" Empire Builder, "Super" Chief). The sets are still the same with the exception that they include the newer DT400 throttle and the UP5 panel (which replaced the UP3 panel). The sets still do the same thing - letting you run the trains without having to worry about flicking power-routing switches.
If the price is right, and the set still works, go for it.
So, it all depends on how much money you want to spend.
Digitrax also produces the DCS100 command station in an 8 amp version. However, it is highly unlikely that most home layouts would need 8 amps as compared to the 5 amps in the standard version.
