The IDA-8 is great sounding product. I've used it as well as the 16. If you are using the 8 with a smaller pair of speakers, say a 2-way bookshelf, it will be fine. Larger 3-way or towers will be very much more demanding. That is where the 16 makes a difference.
That said, I used the IDA-8 with Eddie and Ruby. Ruby was great. Eddie didn't play to its potential. In fact, to be honest - it was not a good match. The 16 with Eddie worked very well.