I'm not sure how well the reseption will be for a whireless ethernet card encased in a metalcase such as a tower.
I'd suggest a drastic aproach where you get extend the PCMCIA port to the back of the machine... either by buying extra parts (or just desolder the existing PCMCIA port) and solder whires between.
Especially in a none Zorro/PCI tower solution you want as much as possible still protruding out the back. :-D
