I have seen it on ebay several times but don't have it. It includes selections from previous Varese releases only and therefore there is no need to have it if you have all 4 previous discs.
I had thought there was a compliation CD released outside the U.S., but also there's an "unmentionable" that has the best of CDs 1-4 and unreleased tracks by Curt Sobel.
There are 2 Curt Sobel promos for episodes he did (fantastic Dracula episode is one of them) and they are IMHO legit promotional stuff that was reused by some bootleggers. Well thinking about it now I am not sure if there are really two Sobel's promos for 2 episodes or two version of the same episode.