Clay King is my favorite supplier. Orders arrive quickly, the stock is fresh, and is packed/shipped securely with no spills or breakages. Have you checked out the 'Sample Packs' for the Coyote glazes: http://www.clay-king...teglazekits.htm ? They include 12 glazes in 4 oz. containers, for around $30 (most of the ones you mentioned are included). I purchased the 'Favorites' pack and love most of them, though I've only used them for a couple of firings. There is also a GIANT pack if you buy directly from Coyote that gives you samples of all of their 96 glazes for around $200: http://www.coyotecla...ample sets.html Too giant for me, I'm afraid I couldn't find a use for most of the gloss glazes. The Shinos are particularly nice.
You might also consider Georgie's glazes, they too have sample packs: http://www.georgies....zes-sculp.shtml ('sculptural' series, mostly mattes) and http://www.georgies....zes-stone.shtml (mostly gloss glazes). I'm trying out the sculptural set right now, they're pretty nice but not too many of them 'break' on texture as much as I'd like.
I haven't tried the Amaco PC glazes, as they don't sell small samples and it's too expensive/risky to buy pints I may never use (I make small stuff like jewelry and tile). The Blue Rutile looks rather enticing, though... I've used some of their low-fire glazes and they're very nice, more 'glassy' feeling than the Duncan or Mayco lines, IMO.
I've only tried Spectrum's 'Low Stone' series for low fire work, but they are my favorites in that firing range. Really, really nice when they are layered. Wish they sold smaller containers so I could try out their mid fire line.
I hope I haven't overwhelmed your choices further, I know it can be a bit daunting looking at all of the options out there! I hope to be mixing my own glazes by next year, but it's been cool to see how certain types of glazes react and layer. It's been a good learning tool until I finally bite the bullet and learn a little glaze chemistry.
Good luck and Happy Glazing!