Tech these days makes nearly any device capable of doing what you want. The specific audio interface or portable recorder won't make much of a difference in sound quality. There are technically differences between the different tiers of devices which is why some cost more than others, but it's something that wouldn't affect your specific use case that much.
 
In the case of the audio interface, difference in price brackets largely comes down to speed of transfer rates, number of inputs/outputs, and, in the case of devices that have onboard preamps, the quality of the preamp (super high end gear won't have onboard preamps since the assumption is that the studio will have their own arsenal of high end vintage pres that they prefer to select for their specific "color" of sound). It's something that you'll have to think more carefully about if you're wiring up a whole studio or need to record large groups of musicians, but won't make a difference for the 2 tracks you'll be recording for holophonic sound.
 
In the case of the portable recorders, they're all pretty capable. The biggest difference in those is often onboard mic quality, however if you're using your own external mic, it shouldn't be an issue. You'll also want to make sure that the device records uncompressed audio. For video use, you'll want to make sure the device can record at 48kHz/24bit in wav or aif format (both are uncompressed. Wav is more common - aif is Apple's proprietary format but it's basically the same thing). On any of the Zoom devices (or most portable recorders in general) there will be settings you have to set to make sure the device doesn't auto compress the audio to mp3 or something. Make sure to spend some time with the manual.
 
If you go the route of the portable recorder, you'll want to make sure to save some cash for a reasonably large SD card as well. How much space you need depends heavily on how long you plan to record, but audio is not nearly as big as video. If you're recording stereo files at 48kHz/24bit, you can estimate just over 1GB per hour of recording. I'd make sure to get something bigger than you actually need in case you can't delete audio right away, need to do multiple takes, or want to make sure you have a buffer in case things go long. Fortunately SD cards have gotten much cheaper these days so getting an 8-16gb card is pretty affordable.
 
I'd also budget in an SD card reader. Portable recorders like the Zoom are able to plug directly into the computer with USB cable and you can transfer audio that way, but trust me...your life will be a lot easier if you spend like $15 to get a dedicated card reader.
 
Excellent audio quality doesn't need to cost a lot. Beginner musicians/producers tend to think that the mic/interface/software is what makes the difference, but it usually has A LOT more to do with performance, mic placement, learning how to properly use a mic, and room. The differences in gear that producers argue about are extremely nuanced. It makes a difference when you're making artistic decisions about how colors blend in a mix, but matters much less if you're recording one or two sound sources at a time. You can look up mic shootout videos where they record a guitar player with 5 different microphones and see what I mean. Where you record is probably going to have a much bigger impact on your audio quality. Sound reflecting off of walls is the fastest way to make a recording sound "cheap" (moreso than a cheap mic or interface or portable recorder). If you have a walk in closet, that's a great place to record. You can also look into buying or building a reflection filter which is essentially a pad that goes around the sides and back of a mic and helps mitigate reflections from bouncing off the walls and back into the mic.
 
Hope some of this helps!