So best route is to go radeon 4 serie, with windows xp? Is the radeon 4 serie strong enough for those next gen emu's anyway?
For mame it does not matter but with other emus like DEmul, Dolphin or PCSX2 graphic card is important. Sometimes not just speed is important but also DX10 or even DX11 capabilities. So the best way would be windows 7x64 here since HD4xxx has DX10. Sadly I don't know what graphic cards will be fine for PCSX2 or Dolphin. On my GRX770 and 4670k DEmul in some places is still too slow :/
Another problem with 7 x64 are some problems with DirectDraw and some emulators. Most of these problems are already fixed but Kega Fusion and OoTake still have problems with switching resolutions. Some time ago Calamity fixed resolution switching in OoTake but this fix was internal (only on this forum) and wasn't probably put in official OoTake and/or future versions.
Personally due some problems with Taito Type X/X2 games and emus mentioned above I stick last time with XP x32 and groovymame 171 but next time it will be windows 7 x64.
Also, if i remember my old cabinet. any game from 640x480 started to flicker.
Under Hd5xxx and newer flickering is still visible but less.
Maybe i should just stick to the basics anyway, just mame old games. This because i want to try a authentik CRT route.
It really does not matter. Any Radeon HD serie card will work fine with low progressive modes like 256x240p just some pre HD4xxx does not support low dot clock modes and for this there is also workaround.
For some time mame officially does not support Windows XP and in future might even drop support for x32 systems so even in this matter Windows 7 x64 is still the best choice.