Should be just fine, but others who've actually tried it can comment. I have not, but do have experience with interfacing consumer and pro gear going back about 10 years.

Nominal output level of the 990 is 1V for a 1kohm input impedance at the amp. Max of 9V line-level output.

Where you might run into trouble is if you mix brands/makes of power amp with the 990. Then level-matching becomes more tricky.