I echo the recommendations to go with the ua5, but if you're set on going the p48 box route, I STRONGLY recommend getting line transformers to go line-in, and would also recommend the denecke ps2 over the 2 p48 boxes you referenced.
If you skip the line transformers go c4>p48>mic-in on the m1, you'll run into mic preamp brickwalling problems on the m1, which will cause your tapes to suffer.