The Numerik is specifically identified by Linn as an upgrade to the Mimik. If you're comparing it to CDPs of the same generation, I think it would definitely get you above the Genki, but I wouldn't expect it to best the Ikemi. Then again, it would be cheaper than a used Ikemi.
However, I think the real question is whether it would be better than the current Linn players, such as the Majik. I haven't heard the Majik so I can't make that comparison.
I'd be tempted; however, given the vintage of the Mimik, and if you have a lot of hours on it, my suggestion would be to save the money and eventually get a more up to date player. The fact that Linn themselves don't make a separate DAC for their newer disc players is significant. (I'm excluding the new converters primarily intended for PC audio applications.)