demonesc :
It would not be powerful enough I'm afraid .
I am not a twitch streamer myself but I have looked into it before and for a good quality stream you would need a powerful CPU and Mid range GPU for a stand alone system.
Or a secondary one for the streaming.
Sorry just saw you intended one for xbox
It is dependant also on the quality of the stream .
For 720p it would not be so demanding.
I'm personally going to use a laptop for streaming my laptop has gtx1050ti and a quad core i5 processor.
Although I have just purchased an RTX 2060 which has its own resources specifically for streaming on a standalone system.
It's a tough one and can't be done very well on a budget.
Also you are looking at a streaming card between the Xbox and the pc ..that alone is like 150 pounds.
The main thing is enough power to process the information quickly so as to not ruin or degrade the stream.
it seems that multithreading is something that is considered vital.
so i would say a ryzen 5 series CPU will give you the best multithreaded power for the best price.
maybe with an entry level AMD rx GPU an RX550 2gb is pretty cheap.
A really informative and useful answer, many thanks demon!
My brother has a streaming card already to put between the Xbox and PC, but from what you are saying it's looking like a budget PC build still won't be sufficient enough to provide a good quality streaming service. It sounds like the quality and stability of the stream is more dependent on the actual multithreading capabilities of the CPU then. I have a Ryzen 5 2600 in my PC but he's not having that, unless he pays me top dollar for it. I don't think 720p stream quality would be such an issue, couple that with the fact that the PC build I have in mind will only need to handle the streaming, so perhaps it could well be possible.
I'll give him the information and we'll see where to go from there. Cheers again for your help.