What a coincidence, but I had the same buying pattern for my guns. I bought a Nova, then decided to upgrade to an AT-85. I really enjoy the AT, it's a great marker. If you've never worked on a paintball marker or aren't particularly "handy" with mechanical stuff, then it isn't a gun for you. Before I got into paintball, I never liked to work on mechanical stuff, so it took me a lot of time, research, and practice to learn to take different guns apart. The Nova was the biggest pain in my butt (Actually, I never should've disassembled it to begin with, but I was curious), and the AT was the most detail-oriented. It needs to be oiled every 500 shots or so, and you need to regularly check for bent/broken parts...mainly the Clip pins and Guide Plate. It just takes consistent maintenance, which is a small trade for such a unique marker. However, don't cofuse this detailed maintenance with overly-hard or time-consuming, as it's fairly simple to maintain the gun. IMO
If you are familiar with paintball mechanics, then the AT-85 is a great buy. It has a great muzzle sound, it never breaks paint (at least when I've shot it), and it is one the most consistently accurate markers I've ever seen. There are a few places to buy it online, and you can get it for a good price if you know where to look. Anyway, this is what you need if you decide to buy:
Starter Kit (manual,video,etc.)
Extra Forward Loaders (unless you use the VL Clip)
HPA tank: This is very important. The AT needs consistent pressure, both to function at high rates of fire, and to assure that the clip pins feed properly. If tank pressure drops below 650-700 psi (which is very common with CO2, especially in high rates of fire or in cold climates), then the clip may not feed properly and you will bend a pin. This can lead to broken paint, timing problems, etc. I've known people who haved rigged nails to replace bent/broken pins, but to me, it's over at that point. It's like $70 to get a new clip.
Secondary Reg (maybe, but not a necessity) The AT-85 functions best from 650 psi to 850 psi, so many preset tank regs will provide the appropriate pressure. A second reg allows you to fine tune your gun to your specifications.
I hope this helps.