Looking for some advice and a budget ITX motherboard for my build

[Mastercake]

I already have an i5 2500K, GTX 670, 8GB RAM, and a 1TB WD Caviar Black HDD.

Which means I still have the following components to purchase:

Primary
• Motherboard
• PSU
• CPU Cooler
• [strike]Optical Disk Drive[/strike]
• Chassis (I dislike plastic cases and side windows - aluminium is the preferred material)

Secondary
• Monitor (perhaps the ASUS VG248QE? @ ~$400)
• Mouse (perhaps the Logitech G9x? @ $99)
• Speakers (Bose speakers @ $149)

I have [strike]~$700[/strike] ~$400 to spend including shipping. Keep in mind I am not looking to buy any secondary components at this point in time.

I am looking for reliable, quality components which do not bottleneck my build, nor add unnecessary expenses (wireless LAN for example). Hopefully you have all the information you need. If not, let me know.

Notes
• I do plan on some light-to-moderate overclocking.
• [strike]Having the freedom to add a second GPU would be nice.[/strike]
• I want 8 (or more) USB slots.
• This computer will be used for work and gaming (mostly Skyrim and The Sims 4 once it arrives).
• My preferred sites are mwave.com.au and ebay.com.au (both national and international sellers). With that said, I would still be willing to purchase from other reputable sites.

 

[Mastercake]

Chassis: BitFenix Prodigy (White) Mini ITX Tower Case @ $85.00
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler @ $39.00
PSU: Corsair CX 600W 80+ Bronze Certified Semi-Modular ATX Power Supply @ $105.00 (I assume 600W is enough for overclocking)
Motherboard: I don't know much about motherboards and need help with this.

Some further notes:
• I no longer need an optical drive.
• I no longer plan on adding a second GPU.
• I don't have much money to spend, my budget for the above components is around ~$300 before shipping.
• I am also willing to purchase parts from pccasegear.com.
• I could increase my budget a bit if I wait a couple of weeks.