Zo, I bought through 'esoundz' and got an extra one of the 5 that way.
Having bought Sampletron last year sometime and getting the 3 plus the one extra from 'esoundz' gives me all 5 now. [Basically I have Sampletron twice if I want it.]
I was running through some of the sounds today in SampleMoog & Miroslav Philharmonik.
If you look at the regular price of $140 each times 5 = $700.00.
For the current price of $70.00 for 4 or possible all 5, that would be just $14.00 each.
So even if you like just one of the 5 packs, [for me that'll be S-Moog for sure], it seems well worth it.
No specific group requirements needed, but you'll have to register with IK's site.
For me I just had a to wait a day or so, and next thing I knew everything was there in my 'User Area' to download, which I just finished installing today .