How can I solve my preamp/DAC/subwoofer issue without spending lots of money?

Setup

I'm currently using an Eskinsin bluetooth adaptor plugged into the AUX input of a vintage Kenwood KR3130 stereo receiver. The Pre-out is then wired into a Rotel RB951 Power amplifier, which is wired directly to the speakers. I also have a **Powered subwoofer** coming out of the mono-out of the Kenwood. This gives me a nice 2.1 system.

Diagram: https://imgur.com/dcwedKr

Current Issue

I was unable to get past 70dB of volume with this setup. I was told by user gs5556 on Audiogon the following:

*I looked at the specs for your amp... the high level setting has an input sensitivity of 775mV. The Kenwood receiver specs show a tuner output of 160mV. That's why the amp is not playing loud, the tuner's max output is -14dB lower than the voltage required to drive the amp to max power.

I'll bet if you put a scope to the Eskinsi output to a 0dBFS test signal you will see the same thing -- an output voltage way lower than 775mV.*

So that leaves me with needing a new way to a) get bluetooth into my system and b) a new way to control volume on my system, since I will be abandoning the Kenwood as a preamp.

The only solution I can come up with, which seems to pay a bunch of money

Diagram: https://imgur.com/5f5G3T3

Buy a new preamp with volume controls (and subwoofer out) with the ability to output enough power and to buy a steamer, namely the Wiim Pro Plus (With built in DAC) to go into the preamp so that I can stream music into my setup, continue to use my subwoofer and also get volume controls.

I think this will work and fix my problem, but at the same time I have spent a total of probably $700 on my setup and I'm really not interested in almost doubling the price for these two items. Is there another way? I would love to hear some other ideas. Thank you!!