Xiaomi 4a is a best budget device in 6k. I bought this phone previous 10 days I am using it and it is a amazing device in 6k .it have lots of good features
2gb DDR 3 ram and 16 GB internal
5 inch 720*1080 screen
Snapdragon 425 processor is quite amazing .no lagging issue till now.
In my opinion redmi 4a is a best budget device comes with lots of good features and build quality also good.
I will recommend to all this device if you are looking for a budget device under 8k