Silabenzene has been made and studied, problem is, it has only been made by flash thermolysis and studied by UV spectrosopy in the gas phase, or by matrix isolation at <80°K.
The problem with incorporating a Si atom into an aromatic ring is a larger one. First, there is distortion due to the larger radius of silicon, the longer C-Si bond length (~25% longer), and second, the C-Si bond energy is ~10kcal/mol less than C-C due in part to Si's increased electrophilicity. (In benzene, all of the C-C bond lengths are the same 1.4A)
A Si analouge of benzene is not truly aromatic. Aromatic (=delocalized pi systems with a continuous p-orbital overlap) sytems are usually planar rings, this due to the carbons sp2 hybridization. The thing is, Atomic Orbital hybridization is pretty much exclusive to the second row elements. This is due to the fact that the 2s & 2p orbitals occupy the same area of space, so that an electron can actually be in the 2s & a 2p orbital at the same time. This due to the unique shape of the 2s orbital which has a node in the center which pushes it farther out. This is due to pauli repultion from the core electrons in the 1s orbital. Third row main group elements such as Al, Si, P & S mainly use their 3p orbitals in bonding (They do have a d-orbital, but it does not participate in bonding). The 3p orbitals do not share the same area of space with the 3s, so hybridization does not occur. There is still p-orbital overlap between the sp2 C's and Si, but due to Orbital effects explained above the Si exhibits weak multiple bond character. It also usually (=not cyclic) adopts a trans-bent geometry due to decreased bonding angles as you go down the Group 14 elements.
On another note...
Perfluoroamphetamine would be fun! It would be volatile as hell, so you wouldn't even have to smoke it, just open the bottle and breath! Perfluoro hydrocarbons are generally pretty inert biologically. Safe, alot are being used in medicine and other fields.
