All these artists have distinct features about their music, even though they may be pretty subtle here.
Astral Projection has very little creativity between tracks, they all sound the same, but they are still great, melodic and nobody sounds quite like them.
Dimension 5 has really big melodies in Transdimensional and then goes really laid back in Second Phaze (totally different albums), but they seem to have more careful constructed layers.
Cosmosis isn\\\'t very similar to either Koxbox or Dimension 5, though there are some similarities.
Also as someone else said, you\\\'ve just mentioned a couple artists here. Maybe if you listed to hundreds of artists you would understand how each of them has varies. Don\\\'t just listen to the most popular things as people tend to worship groups like Pleiadians, Cosmosis, Filteria, for example, which sound very similar to each other (many people don\\\'t care for creativity at all).
Try listening to some of these major artists who sound very different from each other: Jaia, Transwave, UX, Chi-AD, Sandman, Ra, KURO, Moksha, Ubar Tmar, Asia 2001....
Also, try to listen to the whole depth of the music (the nice part about old school goa!) not just the beat, because that\\\'s always going to be the same by definition.