I would like to buy one of the newer classic biplanes that are now on the market. I also would like to have something to use my Saito 1.20 with. I have came down to the following 3 planes: The Great Planes P-6e hawk, the Great Planes Super Stearman and the Cox 1/5 size Waco. I would like anyone that has experience with these to let me know which might be a good match with The Saito and possibly which one would have the better flying tendencies as well as which has the best quality (although I think they all are of fine craftsmanship).

Any of the three you named would fly well with the 1.20. They are all about the same size and weight; it's really a matter of which one you like best (looks). The GP P-6 is a gorgeous plane with its distinctive markings, the Super Stearman is a nice aerobatic performer, and the WACO is........well it's a WACO, enough said. I have the 1/5 Cox WACO, and highly detailed it. I have a G-26 in mine; at 18 pounds, the G-26 is plenty of power and the plane performs very well. The basic ARF is about 14 pounds, so the 1.20 is going to be a good power match. There is a thread here on the ARF forum about the Cox 1/5 WACO and there are several engines being used. Look into it and see what others say.

One thing about all three planes you mention--you might need some nose weight with the glow engine to balance it. The people I know who have the P-6 and Super Stearman both have gas engines in theirs, and they balanced fairly well without extra weight. Even with the added weight, the 1.20 will be enough.

As far as quality, the Hawk and Stearman are both GP models and great quality. The WACO is by Cox, and less well known, but I feel it was about what you should expect, quality-wise, for what you're paying $380 for. I and some other owners are having a few issues, check out the Cox/Pica WACO thread.

There are long threads on all 3 models here on RCU. Run a search.
I have the Stearman with a Lazer 1.50, and it is a good combo, but may be a little anemic with a 1.20, unless it is good strong motor.

How about setting each of these up at the field. How much time, difficulty, etc?

I can't speak for the Hawk or Stearman, the guys I know that have them don't disassemble them for transport. I don't disassemble my WACO either, but it takes me about ten minutes to remove or install both wings in the shop, and I have flying wires on it. Beyond that, a couple of minutes to gas it up and check battery voltage, a minute or so to fire it up, another minute to warm up while I preflight the controls, and I'm ready to taxi.

So far as the Waco's concerned, not much of either.
I do have to take the wings off for transport. But I leave all the N struts and cabanes attached to the top wing, so assembly is simply bolting the bottom wing on, then attaching the cabanes to the fuse and the N struts to the bottom wing. That's 8 4-40 bolts. I haven't timed it, but it's no more than 10 minutes, tops. Less if I'm not shooting the breeze or otherwise distracted.
Don't know about the Stearman or Hawk....