Want access to I2C0 and I2C1.

I am building an audio distribution system that uses a Raspberry Pi to control 6 DACs using I2C. The DAC is a MAX9850, but it is only possible to configure each DAC to one of three addresses. So, on bus I2C1, I have the three DACS, each with a unique address, and all is fine. But now I want to put 3 more DACs on bus I2C0. This where I have a problem.

I have two identical Raspberry Pi 2 Model B. One is the target/production device and the other is for testing.

On the target Pi, I am using the Volumio 1.55 distribution, which is based on Raspbian 3.18.5-v7+. I am unable to access I2C0 on this device. I have configured it as follows:
/boot/config.txt
dtparam=i2c_vc=on

/etc/modules
i2c-dev

When I try this:
sudo i2cdetect -y 0
I can see activity on the SCL and SDA lines on the oscilloscope and they look fine. In fact, I can see my devices attempting to respond (holding bit 9 of SDA low), but they don’t show up on the output.

Meanwhile, On the testing Pi, I tried running Raspbian 3.18.11-v7+. I enabled I2C0 and I2C1 and I can see devices on both buses with I2CDETECT and the application works fine. This is promising, but apparently there are differences between the Raspbian versions that make it difficult to apply the same configuration to an earlier version; but here are the snippets anyway:
/boot/config.txt
dtparam=i2c_arm=on
dtparam=i2c_vc=on

/etc/modules
i2c-dev

So, the obvious answer is to use the newer version of Raspbian; BUT I have seen several threads that have advised against doing an upgrade (apparently because the kernel has been modified); but if I knew how to just update the kernel, I would try it on my testing Pi. Or possibly, if the patch is known, somebody could document how to update the kernel and then reapply the patch. In short, is there any chance of a new distribution of Volumio based on the more recent Raspbian? [and without waiting months for Volumio 2]

I’m stuck now and can’t see a path forward. I welcome any suggestions.

Jake