Brand of DAC converters

Just curious and this may not have any real meaning but I'd like to ask the forum to comment on the differences and advantages/disadvantages of the the various 24 bit/192 khz DAC's that the various CD/DVD component manufacturers use in their audio circuitry. The 3 brands I can find out there are Burr-Brown (now owned by TI), Cirrus Logic, and Wolfson. Are these the big 3? Why one over the other? I cut my teeth on the Burr-Brown with NAD CD players but now I have Marantz which uses Cirrus Logic. My other (Rotel) uses Burr-Brown.

Are there other brands out there? Many of the more mass market CD player manufacturers don't even mention the brand and some don't even mention the type (18 bit, 24 bit, etc) in their technical specs.

Why do some use the term "Sigma-Delta" when describing their DAC chips? Is that another brand or a type of DAC chip? Do any of you purchase sources based soley on this?

Thought this would make interesting discussion. Thanks.