This model wouldn't be a good choice for mining. I'm not even sure their is mining software for it.
This is supported :
http://shop.ztex.de/product_info.php?cPath=21&products_id=74But I wouldn't buy them at this price. At the current BTC price and difficult these quad SLX150 would make ~100/month and it will probably decrease in the following months (at least you can't bet that it will remain at this level).
I wouldn't buy 4x SLX150 FPGAs boards at more than 400-500 and 2x SLX150 boards at more than 200-250.