Amp to pair with Soundblaster Z + Tri i3 IEMs & general questions

Hello!

I’m new here and this is my first post, I’m also somewhat new in general so sorry for any potentially ignorant questions.

Let me start with a tl;dr then provide some context and background for those who care:
I’m looking for a cheap headphone amp to pair with the SBZ and Tri i3 IEMs.

Context:
I’m planning to upgrade from my KZ ZS10 Pros to the Tri i3 and the general consensus seems to be they require more amping than my SBZ can provide. I would like to keep my SBZ to both save money and because I like their software suit, so I’m just looking for an Amp to hookup with this and keep the SBZ for audio processing.
This is my first foray into needing an Amp so I know very little. I saw one guy hook up an amp via the headphone out and heard buzzing through potential “double amping”? So I’ve been looking for amps with optical in and go that route.
I’ve got the FX audio DAC-x6 mkii, Sabaj A2, Fosi audio Q4 and Q5 and the Aiyama dac-a2 as my shortlist so far with the most expensive being roughly £66 on Amazon(UK).
Only the Sabaj and FX audio options are mains powered, the rest are USB powered and I’m skeptical if that’s enough for the power it seems the Tri i3 require?
The Aiyima is only £36 so that brings up even more questions to its ability.
I’ve read threads on the FX audio DAC-X6 (NON-mkii) where it had a jumper on the inside which would switch it between high and low impedance modes if you wanted less noise. I’m perfectly happy with doing some DIY or fiddling but cannot find any sources if the same is true for the newer mkii version.

My two goals are to be able to drive the Tri i3’s and have as little noise/hiss as possible as cheap as possible.

So in short, amp suggestions and any general knowledge you can dump my way would be greatly appreciated. Thank you!