Hi PhilinNMI,
The Symbol G mattresses have 3 models and two of them are memory foam mattresses and the 13" version uses both memory foam and latex in the comfort layers. None of these could be called a latex mattress. Their Gel memory foam uses particulate gel mixed in with the memory foam (see post #26 here for more about the different types of gel foams).
Symbol is a smaller manufacturer that tends to produce some better value mattresses. Factory direct mattresses carries them in their Williamsburg location (you probably already know this) but symbol doesn’t make what could be called a latex mattress.
http://www.abcwarehouse.com/default.asp also carries gel memory foam mattresses made by Spring Air if you want to make a few comparisons. They use a gel infusion in their memory foam which becomes part of the memory foam matrix and can actually strengthen the memory foam rather than weaken it.
Some of the links that I included in post #3 in the other thread would give you a chance to test both Talalay and Dunlop latex in both an “all latex” version and latex/innerspring hybrids. some of these may also carry their own versions of gel memory foam.
Phoenix