Liz,
such a comparison is hard to make while keeping things equal. When I was using the 1070 I was using it throughout, with its final amp.
Now I use the 990 paired with a 7100 amp, and everything is significantly better to my ears, but I cannot tell how much of the improvement comes from the 990 and how much from the 7100.
As expected, the 900/7100 combo is significantly above the 1070 SQ-wise, not to mention the lack of bugs, but again, it's not fair to compare them, they are in different leagues and price ranges.
I've never used the 1070 as a pre/pro only, as you do.
Alex
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Alex