Beefing up the graphics card will certainly help but until you try it its impossible to say whether the CPU will keep up but my guess is that you will notice a difference.
A couple of things to consider.... I dont think your GT630 requires a separate 12 volt feed from the PSU whereas the GTX 950 requires a 6 pin feed.
Check the size as, depending on the make, it may occupy two slots (only plugs into one but covers one next to it). As you mention a 2 fan version this may occupy one slot but will be longer.
Hope this helps.