Without tolerance, the highest I have taken it was 4.5mg with a 1mg redose later on. My best trip on it was at 3.5mg though. With tolerance I have taken it up to 8mg. At that level I got very significant vasoconstriction to the point that it scared me. At the lower levels I get some definite vasoconstriction but not enough to really bother me at all. I did not used to get vasoconstriction from it and I feel like it may have started due to my overuse of it at one point.
I prefer DOC over every DOX I have tried (DOB, DOC, DOI, DOM). That said, I have not had a proper trip on DOI or DOB. I find DOC to be the most euphoric and quite psychedelic indeed, although DOM is certainly more psychedelic (and probably DOB as well). DOC has some wonderful qualities... it doesn't cause much anxiety and the bodyload is generally quite pleasant. And then after the peak, the plateau stage is absolutely wonderful for me... it produces a state of euphoria that lasts for about 16-24 more hours which is absolutely priceless... it's one of my favorite feelings in the world. None of the other DOXs produce this plateau stage for me, including DOM. DOM, however, produces a more intensely psychedelic state, and has a lot of force, like LSD can.
All of the DOXs have a lot of force, though, including DOC. All of them take you over pretty completely and create a fully immersive psychedelic state that you cannot ignore. I find them all extremely visual and they're not to be taken lightly (I'm sure you already realize this however).
So to order them, I'd do:
DOC, DOM, DOB, DOI
And if I were looking for the most psychedelic trip possible, I would put DOM first. All things considered I definitely enjoy DOC the most of the 4.
Oh, and I've also tried DOT... I have not yet had a full dose but I found it to produce a "Beth state" at 3.5mg; that is, it was kind of generic, not pleasant, not unpleasant. It was kind of weird and... bleh. It may turn into something worthwhile at a higher dose.