Can it be done?? The 6db just isn’t enough
Not only you need more gain, you also need RIAA filtering.
We have a basic circuit in our range that does the job
http://www.velleman.be/be/en/product/view/?id=8985
Can I install the K-2573 to the K-8020 on one of the inputs internally
No, we’d recommend to put it in a separate box. For best results, use a 2x9V battery supply.
Series or parallel
18V. series