1. 163Mbps is good enough. Halve your expectation, since no 802.11n device ever performed more than half speed as they nominaled.
Thanks ember, it even works at 216 at times and goes as low as 54 MBps. But I checked the speed and other ping data on speedtest. net and pingtest.net and it is ranked excellent so I can live with this.

2. Try to get rid of the WD backup/encryption partitions on your HDD, they are just useless. Do it with windows disk management or with a 3rd party tool such as diskgenius
http://www.diskgenius.net/download.html.
I used the disk management feature of the windows 7 and formatted it. Will see if it works or not, otherwise, I will use this diskguru thing. Thanks for the suggestion.
3. DLNA indexing problem is not solved in firmware. Dont use it now only if all your files in your HDD is DLNA supported. Unsupported file type may interrupt the indexing.
Did not quite understand what you mean.
4 .NTFS attached disks has only half transfer speed compared with FAT32 disks. Consider which do you need——faster speed
or better compatibility.
The advantage is that you are not limited by the file size. I make videos in HD and so for that need bigger size files to transfer to HDD and so NTFS is best or me. Slower Speed transfer I can live with.
BTW, is there any file format that can support both? I mean higher speed and no limitation of file size.
5. If you want to check your card chip: Device management——right click on your card——Details——in the dropdown list choose“Hardware ID”——copy the shortest ID——google it
I have yet to try this, but I am aware that it supports Dual band, I talked to Dell guys and they confirmed to me.
6. DIR857 has two AR9380 cards for 2.4/5G, so if you need a best performance you should buy a AR9380 PCIE card for you dell, which costs $20. Two same card on the router and you computer will have a good performance.
Good suggestion, I can try that, if need be. I will remember this.
Remember your laptop may only support low profile mini-card (space limit). A normal size AR9380 card is better and cheaper, but usually only MAC designed enough room for it.
I have an AR9380 and experienced above 25+MBps when transferring file from my wireless laptop with a wired 1G card computer. Which means 200+Mbps wireless speed. When transferring with router attached FAT32 disk, the speed fall to 9MBPS.
I appreciate the knowledge sharing.