Which z68 motherboard is best among these for this specs

Of those three go with the MSI Z68A-GD65 (B3), but if you are looking for a board that will be better in the long run, go with the MSI Z68A-GD80 (G3). For the little you pay extra you will have a mother board with PCI-E 3.0, which in the future can save you money (Don't have to buy a whole new PC for better performance). One note, this motherboard I recommended you will have to change the memory rating in the BIOS to 1600mhz!!

I use the MSI Z69A-GD65 myself and am happy with it. I do run SLI. but with a 1155 socket and a i7 2600K with Gskill 2133 ram OC (Quad channel matched kit)

I snoop 2 calls it right on the GD80 boards, however keep an eye on the 2011 socket boards and X79 platforms.

The reason I chose the MSI board I am using is because I can allow it to overclock the CPU safely at 4.2 gig and accomodate the two MSI 580 lightning extremes as well as the 6 intel SATA II and III for a all SSD raid capable of bursting close to 4.8 gig And sustained writes/reads that were fantasy last year.

I used to be a strong asus man, however Gigabyte and MSI have demonstrated to me good boards. The computer I type and browse the net with has a very old DFI lanparty. Still plenty for that task.

Tom's Hardware has been of assistance when deciding on the MSI board earlier this year.

i dont have enough budget to buy x79 cpus..

the i5 2500k will run fine on that board

Gigabyte boards can support on/off charging technology, so you can charge an electronic device through USB while the PC is powered off. I also had an older asus board that could do this. Just make sure whichever gigabyte board you choose supports this function. It should tell you in the details/specs.

For instance Gigabyte's website confirms these 3 models support it.

GA-Z68XP-UD3 - http://www.newegg.com/Product/Product.aspx?Item=N82E168...

GA-Z68X-UD3H-B3 - http://www.newegg.com/Product/Product.aspx?Item=N82E168...

GA-Z68XP-UD3P - http://www.newegg.com/Product/Product.aspx?Item=N82E168...

does asus or msi offers this technology like charging video players when computer is turned off

Asus has "AI Charge" which should be able to accomplish the same thing. I would confirm it's compatibility with whichever board you are looking at through Asus' website. It may require a software solution if what you want to charge requires more than standard USB power output.

MSI has "I-charge" and may require a software solution like Asus & I think it's primarily for ipad. Not sure if it works in a powered off state either.

You should fully research the functionality of these solutions to make sure they do what you want before you decide which brand to go with.