If it is a buzz that goes away when you touch the metal chasis, then that's a grounding issue. Try these steps.
Important: check to see if you are using balanced or unbalanced cables. Could be the main culprit.
-Make sure your interface can used balanced cables.....If so majority of the time this will fix your issue.
If not continue.....
1.Make sure all of your audio equipment is plugged in the same outlet. ( Power conditioner is always a great option, but not necessary)
If they are all in the same outlet......Try moving one of the monitor plugs to another outlet.
If that doesn't work.....Try running an extension cord from a different outlet to see if that side of the house has a grounding issue.
Next check to see if your audio cables are on top of your power cables.....if so separate them.
This is very important to note.....
Does the humming stop when the xlr is unplugged from your monitors? If yes read (A)
If no.....read (B)
(A) IT'S a ground loop issue, and this should help you.
https://www.amazon.com/dp/B00BARTW42/ref=cm_sw_r_apan_i_P8N1GVV6XRPVF8T80SR5
(B) If you are here, that means the buzzing (50-60hz tone)continues with no xlrs plugged into your monitors, which means there is toroidle hum....or transformer hum.... and you will need a slightly more expensive but proven fix.( Less than having an electrician come out)
iFi SilentPower | DC Blocker - Blocks Any DC Offset, IEC Connector https://www.amazon.com/dp/B08XWHJRZ1/ref=cm_sw_r_apan_i_X86VYK8E0DWTY4YXCQCF
Hopefully this helps
This info relates to a 50-60hz buzz/hum
Side note: If its computer noise, thats something different. If you can hear the computer working through your speakers...like if you move the mouse and can hear the sound change, or there is static in the speakers...thats usb ground loop, and requires a different device.
iFi iDefender+ USB Audio Ground Loop Eliminator (Type A > A) https://www.amazon.com/dp/B0849J33T9/ref=cm_sw_r_apan_i_9KN8R470WQ8V5FDZQ9ZY?_encoding=UTF8&psc=1
Make sure you know exactly what you are hearing.....static or buzz.....Then you can select the correct device(s) for the job.
Hopefully this helps.
Sounds to me like you've already made up your mind on the amp. you've done your research and found something that will suit your needs and that's great! So I'm a bit unsure if you're looking for people to say yea good amp or "Get a Katana" (which I'm sure those comments are coming)
As far as your noise issues I'm not sure I understand. Are you saying that there is noise coming from your present setup, which I understand to be the micro amp ?
Are you going to desktop speakers from the headphone jack of the micro amp and then you're hearing noise?
The amp you borrowed, did that noise come from the internal speaker of the amp or are we talking about the desktop speakers again?
I would start with the desktop speakers as your source of failure. A DI is to take an instrument level signal (guitar/bass) to a mic level (to go to an interface or mixing console) it does have a ground switch but if you're going str8 into some little speakers without an interface it won't really do anything for your issues.
Obviously that noise can be coming from multiple sources. If you're on the same circuit as your fridge or air conditioning every time those cycle on that could be an issue. To test this you can move your guitar to different outlets, unplug your fridge ( just for the test, I'm not suggesting you have to unplug it to pratice) See if you can find a "quiet" outlet.
If the power is the problem, there are still a few things you can try. A line transformer like an Ebtech or whirlwind is made to help with ground loop noise on the 1/4" jack side of things. There are also single unit AC ground lifters both if which may help. I've have posted a few links from Amazon.
From the site
The Hum X from Ebtech is a safe and economical way to get rid of ground loop hum. It works by placing the unit on the end of the power cord of the equipment that has a ground loop and then plugging the Hum X into any standard 15 amp outlet. Pretty sure you can get this from Thomann and of course reverb. Get it from Amazon or Thomann and you can probably return it if it doesn't help.
I hope this helps, if you can clarify what these desktop speakers are doing in your configuration I might have another idea but one of the 2 links I attatched may help.
On another note. This micro amp? When connected to the speaker thry Bluetooth there is no latency? Just curious
Check for loose connections. Push all connections in tightly. Maybe even unplug and plug back in snug. Check for over coiled wires. Uncoil them. Check for bunched together wires. Unbunch them. Are there any motored devices (i.e. a fan) plugged into the same outlet or circuit breaker as the audio equipment? If so remove them.
If none of those work, consider these:
https://www.amazon.com/dp/B07W682STV
https://www.amazon.com/dp/B00BARTW42
Good luck