azureskies,
I love popups for camping. I bought one new 10 years ago and used the heck out of it (it literally paid for itself). When I was ready to make a change this year, I flirted with "the dark side" (that's what we popup people call moving up to a hybrid, travel trailer, or rv) but still loved the simplicity and versatility that a pup offers. I hope you can get a popup you love and use the heck out of it too.
My advice will be in general terms.
First, your van owners manual should specify your tow limits and if those numbers require a tow package or not. We still have a Chrysler Town and Country minivan that we bought new with a tow package to pull our old pup with (same bones as your Dodge GC). Its tow limit (and the limit of most minivans) is 3500# with two people. If you carry more people and "stuff", the max limit drops to about 3000#. Our pup was heavy and when fully loaded put us at the weight limit. After a couple brake jobs and some transmission work, I upgraded the Tow Vehicle (TV) to a used Chevy Suburban with an 8000# limit. Message here is don't rationalize too heavy a trailer. You'll end up paying for that decision (literally) in the end.
Second, assuming you pass the weight limit check, you didn't specify if you are looking new or used. We bought new and kept is stored in the unfinished portion of our basement/garage and that is the BEST way to care for it. To get it in/out through a standard garage door means hand-pushing it or using a hand-guided dolly device. You won't be able to use the car to spot it in/out because you would likely only have about 6" of clearance either side like I did with a standard 8' garage door.
Third, looking new or used is your choice. The age in terms of years is not as important IMO as condition. An indoor stored used pup that's 10 years old in great condition as mine was may be a better choice than a 3 year old that has sat outside in the rain when not used. Use the SEARCH function of this Camping Board to find the old threads where we've given people advice about shopping for a used pup.
Fourth, if you are looking new, what TinCanTee said about some pups being the same besides the name is true. You may come across the Rockwood or Flagstaff popup lines which are both owned by a trailer/rv conglomerate called Forest River. One has basically west coast dealerships, the other east coast but they are basically identical pups. Also, StarCraft was bought by Jayco (my old pup was a Jayco) and while there aren't identical, Jayco put a lot of their ideas into the StarCraft line. There are some new companies like Livin Lite that make super light popups (a tent roof, not a solid roof) which would be hard to keep cool I bet even with an AC if it's set up in an area with no shade during summer. You might come across Fleetwood pups if you look used which was part of a conglomerate but the pup line was shut down a few years ago. Fleetwood had bought the old, old Coleman pup line/brand. But since Fleetwood spun it off, you can't get parts for them any more, etc. Coleman has licensed the name to another manufacturer in the last year or two but I don't know anything about them. Somerset is another small line - the Aliner company bought the Fleetwood manufacturing site where they made popups (the two plants were only about 75 miles apart in Pennsylvania) but they are not meant to be compatible with Fleetwoods and I have heard quality/startup problems with Somersets. I would recommend a Jayco new or used generally speaking.
Fifth, look around where you live for what popup dealers are nearby. New or used, there will be times over the years where you may need to buy replacement parts, get the pup serviced, or something. While not necessary, it's preferred you have a dealer nearby who supports your brand of pup. While anyone could perform basic service, getting parts through anyone other than a branded dealer is problematic. Non-branded dealers may service their brands with a higher priority than folks wanting service with non-brands. Since I bought my Jayco from a local Jayco dealer and got it serviced there, I never had problems but I have heard of problems from others.
Last, if you have a 3500/3000# towing capacity, I would suggest you look at popups with a 10' box and no slideout. A 10' box refers to the length under the main roof that goes up/down. Most vendors number their models to indicate size so a Jayco 1006 has a 10' box but a Jayco 1207 has a 12' box - and so on. My pup had a slideout dinette (kitchen table with two bench seats facing) which was great because it provided more space inside but added 500#. Many 10' box non-slide pups with a hard roof will come in around 2500# which gives you a 500# safety margin. Most have 2 bunks which can sleep 2 each and a kitchen table that can fold down and sleep 1-2 to get you to the 6 max people you want.
Although we spend a lot of time outside with our pup, when it's cold, when it rains, at night, etc you will consider the internal layout and features more. Also the forums at
http://www.popupexplorers.com area wealth of info.
Good luck!
Bama Ed
PS - here is a picture of my old Jayco pup
and here is my new pup, an Aliner Expedition (hard sided folding pup only sleeps 3)
I have never towed anything before so I would like to start small (eventually would like to get a trailer). I am looking at it sleeping 2-6 people (but mainly my teenage son and myself). I would like to store it in the garage when not in use (we have a two+ car garage). Which are your favorite brands? Which camper would you suggest for us?
Just because you succumbed to the Emperor doesn't mean I have to. 
It has been garage kept over the years. That will prolong it's life. We used to tow with a smaller vehicle but felt it behind us and we dropped a transmission on a hill with a minivan. We now tow with an expedition. You can tow with minivans but just avoid mountainous destinations
so much, everyone! This thread has been very helpful. And gave me a few laughs. 
