Guess I am the blessed one with access to all three.
my brother has the quest z, nice but a bit bassy. Very god low end punch though. Probably going down to the 23 hz mark easily.
My friend has the request, but its powered by a nakamich av10 receiver so the bass is boomy but the mids are about the best I have heard.
I have the quest and sequel ii, with a sunfire receiver powering them, in a fairly large room 13 by 23 feet.
The quest have an awesome control on the midrange and sound almost identical to the request. The bass is very well balanced and revealing in many areas including the low end at about 25 hz.
Sequel ii speakers are a bit squealing around the 2.3 kHz. Thus a female with high pitch is going to annoy you without proper damping. The sequel ii also lacks mid bass thus a man's lower voice range is kind if missing. A solution would be to raise the height of the speakers so that some of the woofer blends better to your ears,
I would recommend the quest if you have a good amp.
i would recommend the request if you can find them and afford them.
i would recommend the quest z if you do not have a good amp and are desperate.
The sequel ii I would recommend if you have a dead room that is enough curtains to take away the mid highs and of course a decent amp as they need current to produce sufficient mid bass for proper male vocals.
Here is how I would rate them numerically.
Request. - 10
Quest - 9.8
Quest z - 9.0
Sequel ii - 7.5