CT_QuestLevels - Haven't found an ACE replacement, although the FuBar plugin does this for you on FuBar, but I like to see it in the quest window too.
CT_UnitFrames - This gives the units on the mana bar, HP bar, I haven't hid the standard blizz ones yet, but that is next on my list
MetaHud - replacement for DHUD (NOT ACE'd)... haven't got around to trying ICE'd HUD yet
Like Thirsterhall said, try ElkBuffBars - I started playing with them this afternoon, and they are a LOT more customisable compared to the CT version. Just trying to figure how to make the list grow upwards now ;)
CT_QuestLevels - I use FuBar QuestsFu, and keep the tooltip open one the zone I am in - that shows quest level in a tidy little box out the way.
CT_UnitFrames - I never used the CT Version, I always prefered Discord Action Bars, but the ag_UnitFrames are probably about as customisable - I spent ages fiddling with that particular addon!
MetaHud - I can strongly recommend the IceHUD. Again, coming from a Discord background, it was nice and easy to figure out.