I have an SVS SB2000 sub and crossover my R500's at 70hz, the R200 at the same and the R100's at 80. I think it sounds great in my 13.5' x 19' room and my guests seem amazed. Of course none are audiophile types so probably could be impressed by anything.
I do have a nullpoint listening position so know I really should add a second sub in the future.
KEF R500, R200C, R100, SVS SB2000 sub, NAD T758 receiver, Pro-Ject RPM1 TT w/ Ortofon 2M Red, Bluesound Vault2, Sony BDP-S480 BlueRay player, Samsung UN55JU6500F 4K LED TV, KEF M500 headphones, Sony CDP-CE500 CD changer.