Question for Dell Precision Workstation T7600 owners with 8 memory modules

I have a T7600 and my outlet system came initially with 2 sticks of memory. I benchmarked them in Windows 8 and the score was 5.5 for Memory. BIOS showed 2 active channels.

I removed the bundled memory and installed new memory, 4 sticks of the same speed/type. BIOS now shows 4 active memory channels and the windows 8 benchmark is now 8.4. This is a great improvement.

My question is if installing 8 modules goes any higher than 4 active channels in BIOS and/or if the benchmark score improves.

My guess is that 4 is the max number of memory channels (quad channel) and additional modules past 4 will only increase overall memory, but not memory performance.

Can anyone share their experience? If you have 8 modules and have the time to benchmark, then take 4 out and benchmark again, that would be super helpful.