do you have to have it as kit?
i'd go with "heap of NS track" lot (one is for sale on here now) , good locomotive, some rolling stock. basic used power pack will set you ~10$ in LHS, but there is quite a nice one for sale right here as well.
Most kits give you an OK transformer, it will do the job but that is it. A better one for a DC set can be had for ~40 at a hobby shop. Also you will be locked into the type of track that with the kit. If you plan on building a layout flex track will by far give you the most options. As for rolling stock they are only about ~2 a car on EBay. Less if you look for bulk lots (I purchased my best cars this way). As for an locomotive the kit ones are generally lighter and have less pulling power than one bought separately. Get an Athern, Proto 2000 or Bachmann Spectrum. They will last if taken car of. Once again a used one of these will likely out perform a new kit engine.
I would avoid Model Power. I have had two of their locos and they were nothing but trouble. Also I have had their rolling stock and had to modify it to work as I wanted. Their building kits are good though.