It's best to steer away from fans with Led's mounted in them unless you want a showy display, and to apreciate them, you'll be wanting a clear side panel in your case.
Your motherboard probably has two fan connectors, and I expect one is being used for the cooler fan. You can power one more fan from the motherboard, the others are powered from your main power supply, via the 'Molex' four pin connectors.
If you have no spare four pin connectors left on your PSU, 'splitters' can be obtained for sharing a power connection.
It's therefore obvious you should make sure what connector your fan has when you order it. Three pin connectors with three wires attached to fans usually denote the ability for you to monitor the fan speed in the BIOS and Motherboard Monitor (see above).
If you are able to mount a fan in the front of your case, do so, and have it blowing inwards. It's preferable for the fan to be able to suck air in from the front but if you don't want to disfgure your case by drilling holes in or knocking stuff out, the fan will still have some effect by moving the warm air to the exhaust fan at the rear of the case.
And talking of which, the rear fan should blow outwards. The exhaust fan has more effect on controlling temps than the input fan, so you may want to try a single fan exhausting first.
Also, if your heatsink cooler/fan on your CPU came with a thermal pad, it's well worth taking the cooler off and carefully cleaning off the surface of the cooler and anything left on your CPU core, where it mates.
Then use a good heat sink compound, such as Arctic Silver 3, to make good the connection between your cooler & CPU. Instructions for application come with the Arctic Silver and are also available online. Basically they say 'don't use much and don't spill any'.
Using a good compound can have a very positive effect on lowering temps.
Now then, which fan? Higher output (CFM) = cooler temps but more noise (dba). Lower output = higher temps but low noise. It's one of those things like Ohm's law, you can't have one without the other.
As for makes, Pabst and Panaflo are the best, in my opinion, and I've tried quite a few. The YS-Tech 80mm fan is also a goodie, a nice compromise between performance and noise and comes at a good price, around a fiver.
Here's some links. These places are way better than e-buyer. E-Buyer may be cheap but I've had a few nasty experiences with them.
www.theoverclockingstore.com
www.overclock.co.uk
www.kustompcs.co.uk
www.overclockers.co.uk
www.komplett.co.uk
I can recommend Kustom PC's, very good company and also theoverclockingstore.
P & P for Kustom is £2.00 per order, P & P for toc is free.
EDIT: Forgot to mention, all my machines are running at 100% CPU usage, I'm running a project 'crunching' proteins to try and find a cure for cancer, called the UD project. The machine I have running at 54C idles at 46C. My other two machines run maxxed out at under 50C.