Define peaceful! Most large fish, even those that are not considered aggressive, will consume smaller fish that fit in their mouths. Pictus cat are a good example--very peaceful, but very predacious. Most people mean they want a large fish that is not predacious--and there aren't many that won't totally out grow the average 'large' tank.
And that's the key--most of the larger fish just can't be kept with smaller fish. There are many options, but you have to be careful when selecting tankmates. I don't think there are any large, mid-water fish that will be completely herbivorous if kept with smaller fish. So, pick the larger, centerpiece fish that you want, and then select tankmates that will be adequately sized as adults. Angels, for example, can't be trusted with neons, but are typically okay with the larger, similar cardinal tetras.
Most tetras live 4-5 years, IME. On the plus side, you could easily start with some juveniles that will be too small to eat the adult black neons now--but really, eventually, they'll end up being a snack. Contact your LFS and see if they would accept them on trade--many stores will do this, if you're bee a good customer (as I would expect anyone with a 180 probably is!).
Of course, many of the possible fish will also eat the molly and platy fry...