Slackaveli
Headphoneus Supremus
Well, as Ichos said there are also very good D/S DACs. To me they have their place. For instance a good 4490 or 9038 and a tube amp is a great match.You can ameliorate some of the issues with Delta-Sigma DACs by upsampling to DSD on HQPlayer, that's what I do with my my DAC and it helps a lot but I understand most people, even die-hard audiophiles will never touch upsampling because it's burdensome.
But with clean and clear Solid State amps an R2R DAC seems to be a better synergistic fit- as always, your mileage may vary.