I have an NZXT Tempest and I was thinking about optimizing the airflow of the case with better fans. Im also not the big fan of LED lights because i leave my computer on at night and I don't like LED lights flashing at my face.

the case has 2 x 120mm front, 1 x 120mm back, 1 x 120mm side, and 2 x 140mm top. I was thinking about switching all of the 120mm fans to scythe slipstream and realized that ultimately there will be 1 x 120mm and 2 x 140mm more fans blowing the air out than in (not including the PSU). So I guess this is in the end the matter of negative/postive pressure inside the case due to the difference in intake/exhaust. Would this matter? Should I try to keep the intake/exhaust airflow ratio to 1:1? what do you guys think?

it is better to have a higher exhaust presure as this will reduce dust build up.

Front blowing in.
Back out
Side in (prolly onto the GPU= good)
Top out

You can probably get better fans.

I wouldn't worry a ton about positive/negative flow. As long as the flow is good your okay. And dust will happen no matter what, if your a hobby person you blow it out once a month or so anyway.

Petras sell the extremly popular Yate Loon brand (not expensive either) and I use them as many OCers do at the real OC forums (Toms is kinda like Radio Shack). Get the mediums and a fan controller or even the highs if you have temp problems and volt em' down with a controller. The Sunbeam Reobus is very popular and will suit you well.

http://www.jab-tech.com/product.php?productid=4090
Jab-tech is a pretty good place, I have ordered from them.

Petras is the only place that has a direct supply to Yate Loons and there is talk of cheapo labeled ones from other places.

Make sure you have good cable management, it makes a surprising difference for air flow.

OC Forums and xtreme forums, check em out. xtreme forums is owned by one of the most winning OC'ers in worldwide competitions.