Hey Mr.Niceguy, no problem . I am always glad if i can help . Are you using Game Capture, do you have Windows aero disabled?(if not try it out , it gets rid of 90% of the problems with weird feelings ingame)? Which game are you having issues with?
As for your question ball2hi, it depends on what you prefer . Your settings are pretty much close to perfect to get the best quality out of your system / connection. And your stream looks perfectly fine to me (no blur or pixelation even if you turn around fast). A big plus is your low bitrate so chances for a laggy stream are pretty low ( you know , overloaded twitch servers and their problems ;D ). On a sidenote i am really impressed that you can play/stream left4dead2 with your specs , that speaks for OBS (Good work Jim <3 ) since i bet with Xsplit or other alternatives you would have issues / lesser quality.
The only thing you can do is lower you audio codec to 92 to have a tiny bit more reserves for your image quality (but i doubt that anyone would notice). Personally i always prefer a higher Fps stream over better resolution . For example i would prefer a 60Fps 720p stream over a 1080p @ 30fps stream , but thats just me .
So maybe try lowering your audio to 92 or a tad lower and set your bitrate/buffer to 1600 and see if you get high ping if not its fine. Raise the fps to 30 and try the very fast preset to get some load off your cpu. For Left 4 Dead which has quite some high motion scenes, i would recommend a lower "quality balance" setting of around 6-7 to have sharper non pixelated high motion scenes.
(these settings should give you the same quality as your stream now is, but it should look more fluidly due to 30fps and also reduce cpu load!)
Btw , people think the faster the preset the better but it is actually the other way around LOWERING your preset will give you more strain on your cpu but better image quality at a lower bitrate . But if you say your system runs close to maximum i would definitely use the "very fast" preset.