first of all I have to say Iīm not a fan of this fashion synths (Omnisphere, Alchemy) as there is a huge risk of sounding similar to others. Remember, if you like a Patch, 100xxx others may like it as well, especially if it is a workstation like Omnisphere :-) ( I remember this issue with Atmosphere - cannot count the releases using almost the same Sounds or Presets....terrible). For this reason, I always look for synths which arenīt hyped in the market. I can highly recommend "Chronox" by Linplug. You can use your own samples but has also a great library. It includes now the complete content of "Sophistry" which was before released as a separate Plugin, specialized for Ambient/Space. For my ears the sound quality is superb and it is very easy to use and tweak.
A lot of people may not know this Synth and you may ask why! There was an interview a while ago with the header and they ask him the same question. He answered something like this:
"we are not searching for the people like other competitive players do. Our interest is, people finding us and our products for the right reason"
Have to say, I like this approach very much