generally adding fans creates more row..however you could also look at the drive cabling and how it runs,flat IDE cables tend to restrict air flow from front through to rear of case rerouting or replacing with correct type of round cable can help cooling.
Normally if theres only one fan it expels the air from the case at the rear not sucking it in from the front. If you end up with 2 fans then its sucking in air at the front and expelling it out the back is the usual. If you can what I would try is removing the fan from the front and fit in in the back so it blows the warm air out of the case. Also with it being at the back it hopefully would be quieter as it wouldn't be so near you.
I fitted a Freezer 7 Pro processor fan which is controlled by my motherboard, I have a 120 mm fan at the rear, a Trust 'pro psu low noise big fan', this has a temperature controlled fan and an Antec Solo Quiet Mini Tower Case. I only hear the processor fan during boot before the Mobo takes control or if the processor is really busy, 98% of the time the system is practically inaudible.