Z87-G55 confirmed to work with 7x R9 290 (using modded driver from https://litecointalk.org/index.php?topic=11761.0) with Windows 8.1:

http://i.imgur.com/DqXhkvV.png

Getting some blackscreens sometimes though, either when shutting down, booting up or closing the miner. Can't figure out why yet.