You can delete the second set of cats with no ill effects. You will gain a little bit more exhaust noise and a smidge more top end power. Many companies make secondary cat deletes, or "test pipes." FabSpeed and DPS Motorsport come to mind.
I think what your looking for are 100 or 200 cell cats. They can be big $$$.
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-99' Zenith Blue 5-spd...didn't agree with a center divider on the freeway
-01' S Orient Red Metallic 6-spd...money pit...sold to buy a house