Optimal cooling solution for Silencio 550

Hi

So about a year ago I put together my first gaming PC but I haven't used it much since due to work etc. I've only recently overclocked my CPU (i5 2500K from 3.3 to 4.5GHz) and the case I'm using isn't the best for getting rid of heat. The silencio comes with one or two stock fans that sucked so I replaced all of them with coolermaster fans. Here is what I'm using (included links to be clear):

x2 120mm Sickleflow in the front (intake) http://www.coolermaster.com/product.php?product_id=4410
x1 120mmm Blademaster in the back (exhaust) http://www.coolermaster.com/product.php?product_id=6622
x1 CM Hyper 212 Evo CPU Cooler with stock fan http://www.coolermaster.com/product.php?product_id=6741
all in the silencio 550 http://www.coolermaster.com/product.php?product_id=6702

So that's 4 fans in total in the recommended push-pull config. After overclocking the CPU it's about 35 degrees C at idle and on Prime95 the highest it went was 76 degrees. I haven't run many games since but I had it go up to 60 degrees at load after playing on a PS2 emulator for a while. I'm sure that it'd go higher if I played more or different games that used the GPU more etc.

So my question is how might I improve the cooling? I've read this: http://www.tomshardware.com/forum/331629-28-cooling-rou... but I was hoping that someone familiar with this case could give me some advice. I'm loathe to get a water cooling rig (seems too complicated for me - and risky!), so I thought maybe someone could recommend a different config or perhaps how I might swap either model of fan with a better one?

Here's some more info that might be useful:

Specs:

MB: Asus P8Z68 -V
RAM: Corsair vengeance Lp 4Gb x2 kit ddr3-1600 , CL9 , 1.5v
CPU: Intel Core i5 2500k
Graphics: MSI nVidia GeForce N570 GTX Twin Frozr III PE/OC
Audio: Creative Xtrememusic sound card
HDD Seagate Barracuda 500gb, Sata6G, 7200rpm, 16mb cache
PSU: Corsair GS600

I also use Fan Xpert software that's part of the AI Suite that comes with the motherboard to control the fans. It seems ok...