The GPU is pretty outdated, 2GB Vram is struggeling and its deffenitely not top-line anymore, with games being more and more demanding, it will not last you a long time.
Luckely its quite easy to replace it later.
Since power demand on Videocards is lowering you should get a 500W power supply, which was the recommended for your 7870 and it should last you long enough, try to get a 80+ bronze certify on it, any known brand will be fine.
Since you don't have the money for a SSD just get a normal drive and buy a SSD later, hyvrid drives are nice, but its better to just get a lot of storage so you can reuse it later.
A fast I5 should be enough for almost anything since its much faster then the processors in consolers, but in some games with bad optimization they might struggle a little because they have 4threats instead of 8 (console and i7)
ANY motherboard by a known brand with a PCI-e lane for your GPU and a socket for your CPU should be fine!
Try to get a motherboard with 4 ram sockets so you can get 8GB ram, if the motherboard only has 2 slots, get 16GB ram
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