In my opinion, the best possible setup for streaming audio is through an actual soundboard. This requires a lot of setup and equipment to make work, but it's possible to upgrade your setup slowly with the goal of a soundboard in mind. You don't have to get everything all at once basically.
Here is the best upgrade path I can think of for someone who wants to get to the end game, a soundboard:
Samson Q2U - XLR and USB allowing for use with and without a soundboard. Also has a headphone jack so you can live monitor your voice and get a better idea of how your stream sounds.
Ugreen USB soundcards with RCA outputs. You will need up to 4 of these depending on your setup.
Amazon - https://amzn.to/2FVLLuF
You will absolutely need GroundLoop Isolators on every single card!!!! As well as one on your Mic Return from the board for Voice chat.
Best for Return Audio Voice chat/ Aux output - https://amzn.to/32xyGiQ
Best for Ugreen Soundcards into the board - https://amzn.to/2YAtedO For a full soundboard setup get one of these per soundcard you get.
HDMI audio Matrix with Audio Extractor:
This will allow you to capture audio from a game console to your soundboard, as well as give you a splitter for your HDMI.
Behringer QX1002USB, Q1202USB, QX1222USB, x1622usb, x1832usb. These boards all offer different features. But the main thing is you want 4 stereo inputs for mixing sources and compression for your microphone which all these boards include. If you are shopping around take care when selecting a product. Many of the 1202 versions do NOT have compression and do NOT have USB output. Make sure to get the QX1002USB or Q1202USB/QX1202USB at minimum. (The price on the x1832usb has dropped to as low as $250 please check pricing on all boards before choosing. This is the board I recommend as it will cover all use cases and let you do everything you could possibly want to in the future).
QX1002USB - https://amzn.to/3qJCeup
Q1202USB - https://amzn.to/3sS7Pgq
QX1202USB - https://amzn.to/31whSJS
QX1222USB - https://amzn.to/3eFGwNH
x1622USB - https://amzn.to/2YD4DoM
x1832usb - https://amzn.to/3aWGZIY - (My Soundboard)
Cables and Adapters:
These are the cables and adapters you will need to connect everything, you will need multiple cables for the sound cards, and if you are using the HDMI matrix you will need the headphone to RCA cable below:
For a full list of EVERYTHING you will need for a soundboard setup visit my website post here: https://www.thesunnymachine.com/equipment/sound-board-accessories-and-cables/
All that said, the best upgrade you can do right now is starting with the Samson Q2U.
(This post includes Amazon Associate Links)