790GX in Micro-ATX? Why so few???

Perhaps there is little demand for CrossFire in the mATX form factor.

the 780G is ideal for HTPC use, the 790GX adds better overclocking and crossfire for mATX gamers. The proposition is lose / lose in a market that caters to HTPC users. You are asking for them to spend money to release a board that will take away sales from an almost identical model already available to cater to a small enthusiast market...

That being said, I applaud Biostar and DFI for releasing mATX 790GX boards and according to an email from motherboardpro.com, they should have a US release date for the Biostar TA790GX XE tomorrow (1/5/09). I plan on buying one and adding a 4870X2 once prices drop so I am not really interested in DFI's LanParty JR board.

Yeah, some 790gx have ALC889 Realtek audio chip that does DD Live like the old Soundstorm.

There is no 790GX "micro"ATX mb supporting DDL or DTS equivalent (op is asking microATX). There are two 780G mATX mb. (GIGABYTE GA-MA78GM-S2HP [DTS Connect], GA-MA78GPM-DS2H [Dolby Digital Home]). But it's useful only for gamers. (PowerDVD/TMT has a built-in DD/DTS encoder; use AC3Filter for anything else.)