Question need help for a friend that wants to build a system for his "Cloud streaming" system

[spari]

HE has no GPU, and a 10 year old pc.. so wants to update with the. possibility to add a gpu later. He is currently using a gaming streaming service. which seems quite good so far. any ideas on this ? he is hoping to spend under 700 dollars
thanks in advnace

 

[tennis2]

What country is he shopping in? (if USA, does he live near a Microcenter store?)
What monitor does he currently have? (presumably 24", 1080p, 60Hz?)
What computer case does he currently have?