I have found that air shroud is available for 743TQ-1200B-SQ, but it is mentioned only in connection with X8 motherboards.
1) Is air shroud compatible with X9 motherboards?
2) Does air shroud increase noise of the system? If yes, to what level?
The air shroud is designed for server applications w/ passive cooling components. SC743TQ-1200-SQ is a workstation chassis. The cooling fans inside SC743TQ-1200-SQ chassis are not suitable for sever applications. Regular SC743TQ-1200 server chassis acoustic noise level can be up to 52 dBA when all the cooling fans are operated at full speed.
http://www.supermicro.com/products/chassis/4u/743/sc743tq-1200-sq.cfm
http://www.supermicro.com/products/chassis/4U/743/SC743TQ-1200.cfm