I used to have a twin turbo Subaru Legacy which is same IC setup as WRX etc. Top mount is good for short pipe runs and giving reduced lag but it's very easy to suffer from heatsoak at which point the IC becomes essentially useless. On a hot day, in traffic or driving hard it WILL heatsoak, how long before it's useless depends on the temps and how hot your engine bay as a whole is as well. This can be countered somewhat with waterspray setups though but that only works when on the move and you have the added complication of setting it all up. For a fun daily driver though a top mount would work fine and be easiest. You can also look at a water to air intercooler for top mount... slightly more work than a straight top mount but substantially more effective.
Your side mount idea could be easy but you're going to have no air flow and a long and complicated piping setup = lag.
Front mount is ideal but again custom piping, lack of space etc.
IMHO a top mount or a nice water-air setup would be best bet for what you want.