Dish Network doesn't carry much news... not that it is Dish's fault. LinkTV is about the only decent news coverage you'll find on cable/sat as everything else is tabloid or outright propaganda.
As far as movies, just how much do you really want? Platinum is really good because it offers a plentiful cross section of HD films, old (Retro / Sony Movie Channel) to the new (Epix, Epix 2). HBO, Showtime, Starz is more about whether you want to watch the original programming as the movies they show are available to be had other ways before they debut. Top 200 gets you the TCM, AMC, IFC channels. TCM has done wonders with remastering the old catalog of films.
The extra "science" channels (read shows about UFO's, armageddon, whether they'll ever find the ark, is there really a big scary monster in that lake, ghost hunters, lets blow stuff up and pretend thats science) are typically on the Top 250 package. If you have a decent broadband connection, Netflix could be the way to go for $8 a month. They have shows available to stream online, such as The Universe. HDNet has some good nature programming, The Wild Pacific (I believe that is HDNet) and they also showed Planet Earth. They have a nice series in HD doing coastlines. I love science too, but these channels offer little of it.
So personally, I'd recommend Top 200 with platinum, and any particular premium movie channel you specifically want... try it for a couple months, see if you like it. If you want more, Dish Network will gladly take your money in exchange for extras channels, but it is probably best to go knee deep before diving right in.