790FX 790GX 790X

They are part of a series (MA790) that have a wide variety of differences including CPU choices, DDR2 vs DDR3, FSB speed, # of slots, etc... The differences between them are available if you search for "MA790" at any popular M/B sales site or at Gigabyte's site. There seem to be 11 boards in this series. They may all take the PhenomII chip, but some also take down to an Athlon/Sempron and others up to the PhenomII x4. They do all seem to have 4 mem slots and none seem to have built-in GPU that I noticed.

Socket AM3
GA-MA790FXT-UD5P (rev. 1.0), GA-MA790GPT-UD3H (rev. 1.0), GA-MA790XT-UD4P (rev. 1.0)

Socket AM2+
GA-MA790FX-DQ6 (rev. 1.0), GA-MA790FX-DS5 (rev. 1.0), GA-MA790FX-UD5P (rev. 1.0), GA-MA790GP-DS4H (rev. 1.0), GA-MA790GP-UD4H (rev. 1.0), GA-MA790X-DS4 (rev. 1.x), GA-MA790X-UD4 (rev. 1.0), GA-MA790X-UD4P (rev. 1.0)

Try these links:
http://www.gigabyte-usa.com/Search/Search_List.aspx?Key...
http://www.newegg.com/Product/ProductList.aspx?Submit=E...