I don't know what online tools you've used, broxibear, but the advantage of a Spyder-type product extends beyond just colors.
It can create a quite complex luminance curve, far beyond what simple linear contrast (stretch) and brightness (shift) adjustments can do.
I don't get why one would consider a $500 monitor and expect great results w/o using a $50 (used) calibration tool.
Seems to me about the same as buying a D3s putting a 18-55 DX kit lens on it and talking about its great qualities while not having actually experienced them.
EDIT: Just came back to say that last comment was not personally directed at you, broxibear, though I could see how it could easily be seen that way. My apologies. Just musing and playing with metaphors out loud.