I'm looking into upgrading the GPU of my 2019 rig (3700x) and I'm wondering how necessary it is to follow the manufacturer recommendations on PSU. Originally I decided not to upgrade the 8GB GTX 1080 because it simply sufficed my needs and bought a 650W PSU unit.
Fast forward to 2023 it is apparently difficult to pick a GPU which officially requires <= 650W. I'm looking for an acceptable price/performance/longevity combo and the only option right now appears to be the 4070 (not Ti). If PSU was not an issue I probably would have gone for 7900 XT instead, however paying extra 150 EUR for a new PSU on top of that is silly (let alone rewiring everything). PC Part Picker tells me I have some 70W to spare after installing a 340W Sapphire 7900 XT. I'm also limited by 330cm clearance but that's less of an issue.
Any thoughts? Thank you.
If you're willing to risk it and just try it out first with the old PSU then i would definitely try that first. I have the same PSU as you and i recently upgraded to a 6950xt. So far it's been running just fine even though AMD recommends a bigger power supply. I was also using a sapphire nitro+ vega 64 before this, which was also quite power hungry when overclocked and never had any issues. I'm not sure how much power a 7900xt draws though.