Different brands w/ diff. specs be side by side in 2 banks?

[allenw1223]

My new ASUS P5Q Pro http://www.xbitlabs.com/misc/picture/?src=/images/mainboards/asus-p5q-pro/board.jpg&1=1 has Dimm_1 Dimm_2 together as yellow and black and Dimm_3 and Dimm_4 as yellow and black so this is the case where 2 different colors together make one bank, so I have 2 banks.

I have this: 4 GB [2 GB X2] DDR2-800 PC6400 Memory Module Corsair-Value or Major Brand installed in Dimm 1 and 2.
I have to see when it ships to me in a few days which brand it is.

If I add more memory would the new additional single or pair of sticks have to match the ones in the existing slots, (the first bank) ?
Can different brands with the different specs be side by side in 2 seperate banks?

 

[GhislainG]

For dual channel mode, the modules should be installed in the same color slots (yellow if you have 2 modules).

Asus and other manufacturers recommend using identical memory modules. At a minimum they should have the same specs (timings and voltage).