Hi,
Other than the ALO RX MkII. I've actually owned or heard the listed amps at one point or another.
I've owned SE420 and heard ESW9 on several occasions.
Voyager might work with your 425 if the sound sig is similar to 420 but will definitely work well with ESW9.
However, to me I felt that Voyager lacks the extension that RSA amps have, compared to my Mustang, which I sold the voyager for.
Voyager is not suitable for most IEMs imo, hisses too much.
Predator have a dark and warm sound sig compared to Protector and Mustang. And might be too dark for your ESW9?
I use dacport for desktop thus didn't really factor in the need of a DAC in my portable amps.
Currently, I am using Mustang and Protector, with an incoming SR71A.
I use protector with a balanced to 3.5mm female adaptor. It gives my UM3X w/ twag v2 a warm analog sound via my imod.
The SE input of the protector reduces the sound stage, but retains most of the sound sig.
I have yet tried direct balanced input and is curious with the result too.
Mustang is a lot more energetic and exciting. I think you should give Mustang a try.