Stock intercoolers will last many years. They are really in a position where they get very wet etc. There was a seller on amazon selling gt2 rs coolers for a silly price a while back, something like £400 for the pair... I think they all sold quickly so this may be of no help. Perhaps do a search on this.
1. Just with a remap on the stock K16's you'll be approaching the need for an uprated clutch. GT2 Rs coolers to help keep AITs down
2. K16 hybrids. To make the most of them you will need to alter your fuel system. Best to upgrade pump to a walbro 450. Ideally you will want to change injectors as they will be maxed out. You can get around this by fitting a 5 bar fuel pressure regulator. IDCs will still be 90% so not ideal and probably to keep it safe you will not be getting the most out of the turbo's. GT2 rs coolers are still widely deemed to be the best solution at this level.
3. BIGGER turbos. You need to set out a limit here of how much power you are aiming for. If you are getting close to 700hp then it gets more serious, uprated rods, head studs are a must. The fuel system needs some serious thought.
Options are endless but you really do need a target power level and budget. PM me if you like or just speak to the normal suspects, 9e, ES, fearnsport.
As far as hiding it from the wife so long as the car stays the same colour she probably won't notice. :thumb: