...I appreciate some input on the choice of motherboards as this is one thing that I have been going over and over in my head without any resolution.
The Asus H97/Z97 motherboards have the advantage that you can use Fan Xpert 2 or higher to manage case fans in a way that it not available currently with other manufacturers' boards. This only applies if Windows is being used of course. It might be worth considering the Asus Z97-PRO on the basis that it has the second CPU_OPT PWM fan header. This would give two CPU headers plus four chassis fan headers. With the Z97-PRO a combination of the BIOS fan tuning and Fan Xpert can be used to deploy either PWM or 3-pin fans. Looking at the Corsair 550D case, assuming that the side fan positions are not used, there are six possible fan positions - two front inlet 120mm, one bottom inlet 120/140mm, two top exhaust 120/140 mm and one rear exhaust 120/140mm. To give the maximum airflow for overclocking it might be a good idea to plan to fill all positions. The Z97-PRO would at least allow one motherboard fan header per fan position for almost all the chassis fans, as one would be taken by the CPU PWM fan. The CPU_OPT PWM header for example could be used with a PWM Y splitter cable to run two 120mm or 140mm fans, the prime position for this would probably be the top exhausts. The CPU_OPT on Asus boards simply runs with the same settings as the CPU header, it is not controllable separately. But each of the chassis fans could be individually configured.
The Asus Z97-A is the most I'm willing to spend unfortunately. It costs a whopping AUD$195 here and Amazon just would not ship any motherboards to Australia so I'm stuck to buying locally. I am actually also considering the Z97-C (AUD$167) but I'm unsure if it's up to scratch for overclocking and the price difference is not that great.
If you decide to purchase additional fans the Noctua Redux NF-P14s and NF-P14R PWM fan for 140mm and the NF-S12B 1200 PWM 120mm are worth considering. PC Case Gear are now selling the Be Quiet 120mm and 140mm PWM Silent Wings 2 fans. These fans have the advantage of being black. The 120mm has a fairly wide range, about 350 to 1500 rpm with an Asus board. The 140mm has a top speed of 1000 rpm which might be a limiting factor, the Noctua Redux fans can run to 1200 or 1500 rpm depending on the model selected. The advantage of any of these fans is that you could expect idle speeds using the BIOS controls of around the 350 to 450 rpm range, and lower than that if Fan Xpert is used. Fan Xpert could also drop the speed of the 120mm 3-pin fans that came with the case and the 140mm fan from your previous setup, but maybe not as low.
Thanks for the recommendation. I am actually planning to get the NF-F12 PWM for CPU cooler. I think I'm currently using the NF-P14 FLX as a case exhaust fan and am honestly unsure if it should be replaced. Appreciate your thoughts on this.
By the way, thanks everyone for your input. I have decided to go with 4690K/Z97-A combo for reasons already outlined above.