Good job, Jiiri_chi!
Be careful with the "normalize filter" feature in jriver. It can lead to digital clipping. If you're running out of gain, you could use one of the EQs in Jriver and boost the sigal with 4-6 dB. This will sometimes lead to clipping too, but only on hot recordings. If you listen to jazz and classical music etc, you could probably go higher without getting digital clipping...
And if you want to monitor it I can recommend the Al convolver, where you can set the volume control to go to e.g + 10 dB and monitor for digital clipping.