Well there have been a few discussions here on that. But first the theoretical part. You aren't seeing 300Mbps due to MAC overhead and some retries and some other minor stuff. 176Mbps is about as good as it will get. I'm guessing this is UDP result. What protocol is running to the SQL server. I'm guessing TCP, which has it's own overhead as well. TCP causes additional overhead on wireless side. Plus 802.11 is a shared medium for which all stations and the AP must contest and get access to which means additional sharing of bandwidth.
I would suggest that for max speed you get a 7982 or the R700.
To optimize you need to disable 11b rates and use higher basic rates. You can try 24Mbps and see how it works although be a bit careful here to not run into some channel overlap and roaming issues. For this you SSH to the ZD and follow this link
https://forums.ruckuswireless.com/ruc... or here
https://forums.ruckuswireless.com/ruc...
Start maybe with first setting the ofdm-only and the bss-minrate then try other multicast and igmp stuff if necessary.