Quickset is a great idea! Please create it for rb750 and rb751 . A lot of beginners will be able to buy these models if they will be easy to configure. a common task is: connect to ISP (static/dynamic ip, ppoe, vpn), setup of ip-tv, port forwarding (for games, torrents etc.), to configure the access...

Of course it supports MCS15 because it supports 802.11n You are asking something like "Does this car have wheels", and I am telling you "If it's a car, it has wheels, its logical" yes, but if I see picture of this car in a store without wheels, I ask myself, do i have to buy whe...

What did you expect to see there? MCS data rates are the same for all 802.11n devices
You can go and see the MCS numbers here: http://en.wikipedia.org/wiki/IEEE_802.11n-2009

if RB711GA-5HnD support 300Mbps throughput, I expected to see mcs15

Where did you see this? From the R52n-M datasheet:

2Nss: 270Mbps @ 800GI, 300Mbps @ 400GI (Max.)
MCS7 20MHz -77 16

http://routerboard.com/pdf/330/rb711G-5.pdf
only mcs7, and no one words about 300Mbps

300Mbit is only possible with 2 chains. R52n-M has two connectors.

and why in the specification for routerboard has been written mcs7, but if 2Nss then it must be from mcs8 to mcs15?

I rephrase the question, what is purpose of TX in 2 chains in the RB711GA-5HnD, but only with 1 stream ? To get full speed of 802.11n. Only with two antennas, or dual pol antenna, you can get near 300Mbit wireless speed in 802.11n I little bit confused, in the brochure for R52n-M (for example) writ...

I rephrase the question, what is purpose of TX in 2 chains in the RB711GA-5HnD, but only with 1 stream?

maybe somebody can give a link where I can read about routerboard hardware and antenna's use

all the options work, important is what you need it for

If I correctly understand, in RB711GA-5HnD two chains used for spatial diversity.
so what kind of main benefit or disadvantage will be for these types of antenna's connections?

please help to novice. in RB711GA-5HnD specification written that it has 2 chains, it means: that I must connect two identical antennas (like this ), or I must connect only dual polarization mimo antenna (like this ), or I might connect one antenna (like this ) in chain0 and it will be work? What co...