I own a Micronik Infintiv-II tower and all I can say is that it's not some cheap plastic crap...The skeleton of the tower is metal, so no problems there, but the surrounding is plastic plates. It doesn't bother me though :-)
The size of the tower is regullar minitower, and the A1200 mobo only just fits. If you would like to use the PCMCIA port you need a 45 degree converter (if it's not already in there) and Mediator is certanly out of the question, unless you are totally willing to destroy your tower, which I recon you are not.
The best choice for Mediator is obviously Mirage, as they are designed for it, but I have an RBM Towerhawk which I have fitted the slots into, but it took some handywork :-)
As mentioned Elbox' keyboard adaptor takes both kind of keyboards, so mayby your lucky. If you need to buy a new adaptor then buy the Elbox adaptor, and find another way around to make your reset button work (in case you buy the tower).