With a riser cable you could still use that 8th slot in the Silverstone case, but the radiator will probably not fit. In this thread http://www.overclock.net/t/1427960/build-log- … ilverstone-gd07, a 240mm radiator was installed outside the case (with the fans inside), but that required to drill two holes. Additionally a 360mm radiator was installed inside, but that one blocked most of the drive cages.
If tower cases are ok, then you could have a look at the the Lian Li PC-10N, which is one of the smaller ones with radiator support and 3 external drives (still bigger than the Grandia GD07, but better airflow).