Is my motherboard causing my computer problems?

[ShmoTho]

So I recently went on vacation for a little over a day, and me being as smart as I am, forgot to turn off my PC during that time. After coming back, I noticed that my PC seemed to be running slower than usual, and was trying to find a way to find out what the problem was. However, yesterday morning after trying to turn my PC on it would only get up to the bios splash screen, then proceed to turn the screen black for around 2-3 seconds, then have a white line across my screen flicker for maybe a little less than half a second. I have tried to:
-unplug devices from the PC
-run my PC on one stick of ram
-run my PC without my GPU
-reset the bios settings
-boot from a Windows CD (PC did not load CD)
-buy a new PSU and replace the old one
-tried all of the steps above with a new PSU
All of the things I've tried still led to my PC not going past the bios splash screen. From what I have seen online, it appears that it is more than likely a problem with my motherboard, but I really want a clear cut answer on what's going on. Thanks in advance for any input on my situation!
Specs:
Intel i5-4460 LGA1150

ASUS B85M-G

2x4gb Ballistic Sport

GTX 750

Logisys 480W

Windows 7 Ultimate

 

[BadActor]

You have just about ruled everything else out, short of the CPU, and those rarely fail unless damaged by a faulty power supply. I would change the board.

 

[Calvin7]

GTX 750 needs a minimum of a 400W power supply with a +12V rating of 20 Amps.

Logisys 480W is a low quality, low price power supply.
Output+3.3V@28A, +5V@36A, +12V@16A, -12V@0.8A, -5V@0.5A, +5VSB@2A
http://www.newegg.com/Product/Product.aspx?Item=N82E16817170014&Tpk=N82E16817170014

As you can see +12v rail has a 16 Amp rating. Cheap power supplies like this have their wattage on the +3.3v and +5v rails.

(watts equal amps times volts)

power supply has 12 X 16 = 192 watts max power on +12v rail.

 

[ShmoTho]

GTX 750 needs a minimum of a 400W power supply with a +12V rating of 20 Amps.

Logisys 480W is a low quality, low price power supply.
Output+3.3V@28A, +5V@36A, +12V@16A, -12V@0.8A, -5V@0.5A, +5VSB@2A
http://www.newegg.com/Product/Product.aspx?Item=N82E16817170014&Tpk=N82E16817170014

As you can see +12v rail has a 16 Amp rating. Cheap power supplies like this have their wattage on the +3.3v and +5v rails.

(watts equal amps times volts)

power supply has 12 X 16 = 192 watts max power on +12v rail.

Thanks for the your comment, but what your saying is that I need a new PSU? I also am only running my PC without the GPU, so the wattage is definitely not the problem in what I am asking.