The Z400 is what I want to get, though I could buy two cheaper quads (one for me, one for the wife) for the same price. I like the Z because it has reverse
One the cheap end of the scale I'm thinking about a Kawasaki Mojave 250 for me and a Bayou 220/250 for the wife. I've always had a soft spot for the bayous because my neighbors had one growing up and they had that thing for like 20 years. I could get both in decent condition for around $1000 each, which is very enticing. The big problem with the mojave is that it's kickstart only (which I don't mind), but the headlight kinda sucks because there is no battery.
Other quads I'd consider are Yamaha Warrior (heavy, but proven), 400/300ex (pricey compared to similar quads), raptor 250, etc.