Based on my experience if you get either the beolab 8000, beolab 6000 or beolab 3 series which are the lowest cost options you can buy used, you would need subwoofers will all of them! I have owned all of these speakers and they all need subwoofers without doubt. For the beolab 8000 and 3 you can use the BL 2 which is also available at a decent price used. However, the BL 2 are too powerful for the beolab 6000, for that you can use a BL 11. I have it set up mine with the BL 11, but they are not very good subs for movies.
I have also owned multiple generations of both the 8000 and 6000 series of speakers because I love their design. I found a significant difference in sound quality of the speakers I bought in 2010 and those that I bought in 2004. The 8000 and 6000s I bought in 2004 were both damaged by late 2009. The 8002 and 6000s I bought in 2010 are still performing like new. The bass also seems better.
However, your best bet is to get a new Beosound Stage since you will get the full Atmos audio experience with your Apple TV. If it we me, I'd get the Stage, but I am not sure it will look as nice as the BeoLab 8000/6000 with BL2 set up. The BL 3 on floor stands can look good too.
Used BL 9s are competitively priced as well.
My 2 cents worth :)