'4 x DIMM' Confusion

I currently have an ASUS Maximus Formula with 4GB (2x2GB) DDR2 RAM and Q9400 ruing @3.6 GHz.

I am quite happy with CPU performance and I want to upgrade my graphics card and RAM as 4GB is not really enough for today's applications/ games. The problem is that on the specification of the motherboard it states '4 x DIMM, Max 8GB' and then it goes on to say 'Dual Chael memory architecture'. On the actual motherboard it is clear that there are 4 RAM slots, but I am just sceptical as to what it means by 'Dual Chael memory architecture' on the specification.

The question is, if I bought exactly the same model of RAM (two more 2GB sticks) would my motherboard actually support it? Also, my current RAM is overclocked @450 MHz, and if I started using quad chael configuration (4x2GB) instead of dual configuration (2x2GB) would that affect the overlooking at all?