Canon Eos 5D Mk2 / Mk11 Noise at High ISO's

I have just returned from a great wedding at LLangoed Hall Hotel in Wales and it rained all day. It was very dull all day and I used the 5D at ISO 1600/3200 most of the time. The group photographs had to be arranged inside with very little light bouncing around a large room. The largest group was 15 Guests and the ceiling was about 12 ft off ground level. I thought to myself I wish I had a new Canon eos 5D Mk II with low noise at ISO 3200. But I have got the good old Mk 1 and had to use ISO 1600 with F5.6 Shutter 1/60th and a canon 580ex Mk II with large Gary Fong Light sphere Diffuser. I use this  set up quite allot for winter indoor group shots and it works well. The 5D at Iso 1600 is good and the recycle time of the flash is reduced by the high ISO. The light sphere spreads the light all around the room and makes it look like flat natural daylight. I hope the 5D MkII noise level is cleaner at ISO 1600 than the 5D as this will make a difference to me when using this technique.

rb