Littledog [/i] [B]I'm not sure any good piece of gear will really warm up thin vocals very much. If your vocals are really thin said:
You're looking at the wrong thing... compression and outboard units won't "thicken" a thin-sounding source - you either change the source, or change the way you're recording the source.
For thickening a thin voice I would look at some flavour of cardioid mic (for example a C1 or a 4033) and take advantage of the proximity effect by moving in closer to the mic than you otherwise normally would.
You're misusing the word "color" in the context of gear applications. The fact that the RNC is a more transparent compressor than others will neither help nor hurt your issue of "voice thickening"....
Same thing with going for tube gear (or in this case, "faux-tube") -- tube gear alone is not going to thicken anything, it's all about understanding the basic problem and the right way to fix it.... in this case, your solution is recording technique and not so much outboard gear..........