Radeon HD 7700 Ghz Edition would be great match to Athlon II X2 270, if you can find it on sale somewhere. Anything better than HD 7700 would bottleneck the CPU hard, e.g GT 1030.
In my AMD build (full specs with pics in my sig), i have Athlon II X2 250 and Radeon HD 7700 Ghz Edition. I keep that build around for retro gaming (games pre-2005) and it handles old games quite well.
Though, Radeon HD 5450 is way too weak for Athlon II X2 250 or 270 to make the PC suitable for gaming. I had HD 5450 in my AMD build before i upgraded GPU to HD 7770.
For PSU, any Seasonic unit in 500W range is more than enough. E.g: M12II-520 EVO, G-550, Focus 550 or Focus+ 550,
pcpp: https://pcpartpicker.com/products/compare/TgW9TW,DPCwrH,bkp323,KmgzK8/
Focus and Focus+ are the newest PSU lines from Seasonic and they come with 10 years of OEM warranty. G and M12II EVO series PSUs come with 5 years of OEM warranty.
All my 3 PCs: Skylake, Haswell and AMD are also powered by Seasonic.