Volt is still in toy class, no offense.
The less than 4 channel Volt units do not have all of the same features IIRC.
I guess it depends if he wants noticibly lower quality to save $200. I'd pay it knowing I got a top of the line interface for an interface by chance that I didn't need all the pres the 4K unit comes with. In a sense he is getting a $4000 unit for $500.
If he gets the Volt he is not getting the benefits of a 4K interface; instead he's only getting exactly what he's paying.
As I’ve stated elsewhere on the forum, the onboard preamps on most interfaces simply do not compare to good outboard.(your Focusrite ISA rack is likely higher fidelity than these interfaces, for example)
So, the X series has better preamps. Excellent. And good for most people to learn the value of quality preamps. I have no issue with that. Having an 1176 style compressor placed in front of each of four good converters is pretty tasty sounding to me. That’s the reason I like the Volt 4 channel, because I’d likely bypass the preamps anyway. Running a good pre into an 1176 style compressor, and then converting to digital is something that I do regularly for vocals and bass. It was a huge step in the right direction for me. The vocal chain for the song you were so kind as to take a stab at making better was: handheld Shure SM7b to UA 6176(a UA 610 pre and 1176 style compressor in a 2 space rack unit) to a line in(bypassing the pre) on my Soundcraft mixer interface. That type of compression use is not easily emulated in software, as it takes place before digital conversion, and takes full advantage of available bit depth/headroom. I have done it both ways, and find that I like that approach over plugins for vocals, bass, and drums(especially kick and snare). I’m not saying “crush everything“, but just enough of the spice needed for the task at hand. This is something that I wish I had learned long ago.
That said, I also like the SSL unit, posted by the OP
@ibmorjamn , because of the good rep of SSL, and the additional option of using outboard converters and preamps via ADAT. Although the SSL only has ADAT in. As a UA fanboy of late, I would likely save up, add one of these to the cart before checking out….
..or find a mint used one, or whatever. It has an ADAT interface, and UA conversion onboard for four more external preamp channels.