I find FPS mainly only gets your BB to the target faster, and in some applications, higher fps will actually REDUCE your accuracy and range.
I've seen well built 310fps AK's outrange 470fps stock sniper rifles.
And my VSR gets better accuracy at 328fps on .3s than it does at 380fps on .3s
You can increase the range on a stock gun significantly buy just buying a 6$ hopup rubber. Raising the fps on a stock gun usually doesn't do anything other than raise your fps, and often reduces the life of your stock parts.