i’ve found it hard to match all 4 items every time with any one maker. If you like kits I’d suggest the lifelike proto 2000 cars, but these are not shake the box 10 minute models. Athearn Blue box, intermountain, & McKean are some of my favorites. Still I change out wheelstes with LLp2k metal sets and check weight and coupler height religiously.
Don’t forget the Branchline kits. Both styles - the Yardmaster kits are really no more difficult to assemble than an Athearn blue box kit, but the detail is much nicer. The Blueprint series take a bit of time and patience with all the individual grabs and so forth, but are worth the effort.
Both have metal wheels, body mounted Kadee-compatible couplers, and come in pretty close to proper weight. And they are generally highly accurate models. They don’t just slap any old paint job on these things.
Walthers also have good cars in both RTR and kit form - most of these are designed to use Kadee #5s as a straight drop-in, though some need offset couplers (the 5-unit spine car needs #47s). I would advocate fitting metal wheels to these, but in my experience they’re usually well weighted - Walthers use diecast bodywork on their intermodal cars to add weight. Worth a look if you’re modelling modern equipment.
All except the cheapest brands have body mounted couplers, but in many cases they should be changed to a better quality one or different style. Also, most kits come with plastic wheels, which can easily be changed to metal wheelsets. Nearly every kit requires additional weight, although AccuRail is close to being correct.
Ready-to-Run models that meet your criteria are Atlas, Proto 2000, and some, but not all, Athearn. Athearn Genesis are better than plain Athearn Ready-to-Run. Walthers models, too, come in different quality lines.
I have tried an acurail car, and was pleased that the weight and coupler height were good, the trucks roll pretty good. Any cars that score this good or better are great.
At this time I don’t wi***o replace wheels on brand new cars, and plastic wheels are not a problem if they work right.
Slightly difficult assembly is not a problem.
All my old Athern cars require shimming for correct coupler height.
i still like the athearn rolling stock even if i have to rebuild the couplers…for the money they are the best …even the trucks on them are good…I’d stay away from the red caboose stuff…I purchased a couple of them and they just don’t look right…the bodies ride too high above the trucks and they just don’t look that prototype with the high bodies…Chuck[:D]
If you want to make Accurail cars even better - drop in some Proto2000 metal wheelsets. I did that to all my Accurail cars (and a couple Red Caboose kits that came with Accurail trucks) and they roll incredibly well. I picked mine up online from M.B. Klein, http://www.modeltrainstuff.com where they are only $3.99 a pack - each pack does 3 cars! Well worth the cost! Metal wheels sound better, roll better, and help keep the track clean.