867 mbps is pretty good. Most of your clients are not going to support the very high throughput data rates.   You need wifi adapters that support 3 or 4 spacial streams which are pretty rare.   Check this out for channel width and spacial streams cor...

This is an interesting question. Are you sure your APs support TX power of 30 dBm? That seems very high especially on the 5 Ghz spectrum. The max TX power of Cisco 3802i's is only 23 dBm on 2.4 and 5 Ghz. To answer your question think about this: If...