Ok, I'm going to upload my pics from my phone to avoid photobucket hassle, and then I will edit the post with typed words via computer because it will be a long explanation of what you're looking at. Try and reserve judgment until I put the information in, so as that some questions that you will inevitably have can be answered first.
Ok, here we go-
This is the two tires laying down flat on the ground so that you can get an estimate of the width difference of the wheels that I'm working with. The spare is a 16x6.5 ET 50, so all of my spacer measurements were based off of that to compare.
This is the amount of bulge that comes out past the wheel rim, roughly 15-16mm. You can measure yours to get an idea of how much different your tires are to this spare. They should have less due to the fact that your wheel is 1/2" wider, but I don't know what that is going to equal in real world numbers.
This is a front end shot of the front wheel. It is not perfectly parallel to the car, but should give you a rough estimate of how much tire is sticking out.
This is a 1/4 shot with me sitting on the front end. This should be *roughly* where your car will sit in relation to the tire when on Sportlines.
Same shot, a bit further back-
When I threw my 10mm spacer onto the nuts holding the 15mm adapter, I get 15mm (measured from inner spacer lip to outer spacer lip)-
This is the first of the pics for the rear. This is a 15mm spacer on top of a 20mm adapter-
Rear shot, closer to parallel than a 3/4 shot, with suspension compressed as much as I could get it-
Rear 1/4 shot with compressed rear-
Ok, the math. You have 17x7 ET50 wheels and want a 25/30 spacer setup. This puts you at a ET25/20, which gives you a total of 63.9mm of poke in the front and 68.9 in the rear. I have 16x6.5 ET50 wheels with 15/20mm adapters already installed. The closest that I can get to your total poke measurements with this wheel is to add 15mm of additional spacers. This puts me at a total ET20/15, which gives me a total of 62.6mm of poke in the front and 67.6 in the rear. That means that these pics are mathematically all 1.3mm inboard of what you will ultimately have for wheel fitment.
The numerical poke number is in reference to the outer edge of your lip in relation to your hub. This has nothing to do with the tire, per se, other than the fact that your tire has to mount to it. If you take a measurement of your tire bulge in a similar fashion to what I showed above (lip to outer edge of bulge), then you can remove the 1.3mm difference (stated above) and any additional amount is savings that you would have from your tire to the body. A rough example to illustrate would be to assume that your lip to bulge measurement was 11mm. 16-11+1.3=3.7 That means that you would have an additional 3.7mm of clearance in comparison to my pictures.
To better illustrate the differences that a tire can make, the 16" wheel with 30mm of spacers (as pictured above) is exactly 1mm farther outboard than my 18" wheel with 15mm of spacers. Despite that 1mm difference, the tire bulge you see above in comparison to my 18" pic (further up the thread) is drastically different. Fwiw, the bulge on my 18's measures only a few mm, and that is near the wheel rim. Like I mentioned earlier, the PS3's taper in from there to the tread.
Honestly, I'm curious to see where your wheels end up after the drop and spacers. Honestly though, I don't imagine that the tire fitment will be there. A few mm will save you in the rear if you keep you don't remove the camber induced by the drop, but only a tire change is going to save the front. I think your 17's are better fit with a 20/25mm set and possible fender roll. What I've seen today combined with number-crunching, there is no way that this could be run on the streets without causing some damage to the body. Obviously this doesn't take into account what your tire-bulge number is, but you would have to have a pretty small number to make your tires not hit anything.
I would appreciate if others double-check my math and post any issues found. Ask questions, add input/advice.