I agree with the Synthmaster suggestion. The Nori banks have almost exact copies of synth sounds from YES, Return to Forever, King Crimson, etc.

Of course Omnisphere is a great synth, but it costs a lot and may not have exactly what you want.

Is there an echo in here?  LOL... 

Well, for $9 how can I resist! In fact, I’m not sure I want/need to do much editing anyway. If I like the sounds and then find I have a burning desire to edit I can always get the full blown synth.

Hmmm, maybe get SynthMaster Player AND Omnisphere...LOL!

My advice pointing you to Synthmaster was based on your stated desire to create "exciting synth leads". Omnisphere can do that, but it's not its forte. Personally, my default for such tasks is Zebra, but that's more expensive. Plus you said "prog", and when I think "prog" I think classic synth leads by the likes of Rick Wakeman and Keith Emerson. Synthmaster does that stuff very well, as evidenced by Nori Ubukata's spot-on emulations.
 
But then later you switched gears and asked about pads. Had you led with that question, I'd have said "Omnisphere!!!". Pads are what Omnisphere was made for.
 
Well, technically it's what Omnisphere's predecessor, Atmosphere, was made for. But all of Atmosphere's great pads are still in there. Plus Omni's got some really sweet organic string pads, classic synth strings and choirs that are most definitely prog fodder.

Something else to consider if you save bucks by going with Synthmaster: take a look at Gforce Mtron Pro. If you're already doing some strings, then the classic sound of a mellotron will really give you that classic prog sound of Yes, Crimson, Genesis and many others.

True, that GForce M-Tron Pro is the best mellotron emulation I know.

The thing that really amazes me is the stuff that KV331 gives away for cheap.  It is a quality synth that stands strong among the lists of the best VST synths available.  They really should raise the prices to be more like u-he, and avoid the discounting...
 
If SM 2 cost more, it would certainly be a tougher decision to choose between u-he Zebra 2 and SynthMaster 2...
 
But as it stands now, SM2 is the best deal available for the money!

My stuff really has less to do with prog.  I am into rock/prog but  "My stuff is more like laid-back rock/fusion ... sorta."  It's hard for me to put a label on it.  I like classic synth leads but also like the big synth pad sounds of Yes and the like.  But again, I wouldn't say that my music is prog.  Mu music is all guitar oriented instrumentals with string/piano/synth rhythms as well.

Look forward to hearing it!
Best

Unless a person is extremely particular about those old analog sounds in the Moog,Oberheim and Prophet 5s etc.. I tend to find emulations of those all over the place. They might not be exact. So close my ears can't tell in a mix.I don't think I've ever heard an emulation so bad I would reject it. That includes the sounds in my keyboards that are digital copies of analog sounds. Even Kontakt basic library has some decent keyboards in the rock section.
 
The Hammond B3 though, if you're trying to emulate that one there are some bad ones out there. Even so, putting an emulation under guitars at -3db I hate to say most won't be able to tell.
 
 
You guys have me curious about SM2.