Creature Collection Revised, while it didn't get rid of all the warts and knobs from the original Creature Collection, is still an improvement and worth considering - it all depends on how many monsters you may use out of the original Creature Collection. If many, pick it up. If only a few, it may be more worth your while to scour the web a bit for those specific creatures revisions.
The Ghelspad hardcover's good, though seeing as how you have the gazetteer, not as important. I do, however, recommend the Termana hardcover or gazetteer. These are two of the more outstanding Scarred Lands books. Lost Tribes, though...eh. Luke warm on. Maybe it's just the fact that I read fewer RPG books as of late, browsing mostly, but after owning it for a year, I still haven't read past the first ten or so pages. Furthermore, the dragon stuff in Lost Tribes has an Asiatic feel to it; this may or may not influence your opinion (for me, someone who liked the Greek/Mesopotamian feel to the initial few Scarred Lands books, it turned me off).
Relics and Rituals II, meanwhile, has a few nifty bits of setting material in it involving astrology.
If you like the way asaatthi are presented in the Creature Collection or pretty much most of the other Scarred Lands books, don't bother with Vigil Watch: Asaatthi. It pretty much disregards the original concept and makes a new monster. Of course, it's hard to argue with "free."