Intra,
You want
THIS if you intend on running 160 hub spline hub with a 180 diff. The downside is you need the 180 drive shaft ends to go into the diff & adapt onto your existing 160 drive shafts. As you have rightly said though, you need bug eye or 03 180 drive shafts if you want to retain the 5 X 100 PCD. Finding 180 drive shafts that have snapped (in the center) so you can use the stubs could prove difficult & I'm pretty sure (when I was looking anyway), that the 180 shafts are around $150 each & the hubs will be similar in price each from the 5 X 100 PCD STI. You will also obviously need tail shaft work also, not sure what car you have but generally I believe an auto shaft works.
I have a 6 speed with auto shaft, running a R180 (3.9) , with the linked conversion from R180 diff into R160 hub spline. I am now pushing a decent amount of power through it & have not had any issues yet. I know that it is a weak link though & I choose not to be a muppet & do rev limiter launches.
Full R180 conversion would be the best option, although possibly more expensive. To be honest I with I had done that, but I purchased my complete rear end from another member on here.