You can produce amazing atmospheric or soundscape type sounds with any synth. You do not need a special synth to do it at all. In fact it is better to construct your own ambient or atmospheric tracks yourself by building lots of original sounding interesting layers yourself and mixing them that way.
Pressing one note down in Ominsphere with a great atmospheric sound is not the way to go because you have in fact done nothing to create that sound other than listen to presets and choose one. Also every man and his dog also has that sound so beware. Editing that sound of course is a good thing to do but if you are using stock atmospheric sounds then you are really doing nothing and there is nothing original about doing it that way.
Brian Eno
(master of ambient and atmospheric soundscapes) actually says in one of his documentaries that you only actually need a
dozen or so synth sounds to be able to create anything and I tend to agree. Having too many synths and sounds is actually a hindrance not an advantage.
Komplete can easily create highly original ambient or soundscape type pieces. You have all the tools to do that, it is just how you go about it that is important. Plus it is loaded with bread and butter sounds too. So in some ways you have got the best of both worlds right at your fingertips.
If however you are loaded with bread and butter sounds already and want to get into atmospheric type tracks then maybe Omnisphere is the better way to go. I am sure it is a beautiful instrument. The thing for me with Omnisphere would be really learning it and creating my own patches. Using the existing patches to backwards engineer how those patches were made in the first place as well would be the way to go too.
Your creativity and cunning easily out perform any instrument that you may own. Heck I even heard a great ambient piece that Craig Anderton did with just guitar and weird spaced out effects and it sounded like something Omnisphere would produce so it just goes to show it is the ideas and process that are far more important. I have produced incredible ambient tracks just using sounds found around the house and done some tricky digital manipulation to them.
If you get Komplete I will give you a copy of my DX7 library which is over 7500 patches now in size and loads directly into FM7/8 of course. There are some pretty weird spaced out sounds
(as well as great bread and butter sounds) in that library as well. I have got every DX7 sound that was every made I think and once you start auditioning them you will realise what an incredible instrument that was even for its time. Another good thing about Komplete is the fact that some of those instruments actually sound quite different from each other and I am referring to their sonic signatures. With Omni you will be getting one sound more so compared to a whole range of sound signatures with Komplete.
The synth itself will not turn you into a great composer. Only you can do that. If your music is great then it will still sound the same using any synth. Some synths however are very inspiring to listen to as well and that also needs to be taken into account. Camel Audio
Alchemy is one of those for me. That is a very special instrument too and does things and sounds like no other as well. Especially the groove based material. Talk about amazing!