I want a Diesel Locomotive to perform as a Work Car on my Layout, and I was thinking about purchasing the Dash 8 or Dash 9 Locos, I just need to know if they very powerful. Thanks
Second that yes! all of the DASH-8 and 9 models I'm aware of (Athearn, Bachman, Atlas, Kato) are very heavy machines with lots of pulling power.
Stick to the Atlas or Kato Dash 8's and 9's. The Bachman Dash 8's I believe were out before the Kato and Atlas ones, and there has been some "quality" issues around some of the Bachman diesels.
Athern Dash 9's are good loco's as well, and with a little investment and time, you can re-motor, detail, and add ditch lights and end up spending about the same price for a Kato. Upgrading is a reletively minor job, and it's a great starting project if you're looking to eventually build your own loco. I did three Athern Dash 9's (two UP and a Santa Fe Warbonnet), and they look almost as good (and run just as well) as my Santa Fe Kato.