Hey subbu venkat

Maybe the OlinuXino A13 Wifi is something for you.

It's a ARM Cortex A8 Allwinner based Board, but look here on your own 
https://www.olimex.com/Products/OLinuXino/A13/A13-OLinuXino-WIFI/

There is also a Wiki about this Board (more or less about Software, but 
Hardware and Software are full open-source)
https://www.olimex.com/wiki/A13-OLinuXino

and a Forum is here https://www.olimex.com/forum/index.php?board=2.0

Maybe you look also on 
https://www.mikrocontroller.net/articles/Linux_Boards
There are more Linux Boards.

I would not take the Raspberry PI, it's made with an old processor.

>I would not take the Raspberry PI, it's made with an old processor.

Which is largely irrelevant.
The delta between ARMv6 and ARMv7 is small.

> There is also a Wiki about this Board (more or less about Software, but
> Hardware and Software are full open-source)
> https://www.olimex.com/wiki/A13-OLinuXino

There is no opensource driver for the Mail400 GPU, just a framebuffer 
driver which doesn't bring the GPU even close to it's limits.

Cheers,
Tobi