i don'tthink thermo control is worth bothering iwth. ussually the range of control sucks. unless you engineer something with all the other components in mind, thermo control is kinda iffy. generally the ranges are wrong for any useful speed changes to happen. your better off just making sure you have enough cooling at low rpm instead of hoping the temp sensors get tripped once they hit a high temp.
get a good case, like antec/chieftec, or mod your case. cut out air restricting fan grills, cut big fan holes etc. lots of big low rpm fans move a ton of air, unless it hits 110+ degrees f in your room allof a sudden, nothing should bother your system.
i have vantec speed controllers on my comp.