You'll regret removing sound deadening. Maybe not initially, but it's gonna seem like a sh*tbox after a few weeks. These are nice cars when they're running!
Removing the underhood sound deadening also will make the hood extremely hot (you may not care) and the engine noise might be a little more prevalent. Instead of stripping your car, just add some real power, nice brakes, and some iPd swaybars to counteract the weight.
I have the same car as you and I am in the same process of trying to reduce weight. Haha many people on this forum bash on the idea and suggest making more power to compensate for our overweight cars, but weight doesn't just hurt acceleration but handling and braking as well. 1. SEATS!!! these things weight a ton. You can easily drop 100lbs depending on which seats you choose. 2. Battery. there are many aftermarket lightweight batteries out there that'll save you around 20-30 pounds. 3. Sunroof- When i had a 98 honda prelude i welded an aluminum panel in place of the sunroof and dropped 45 pounds, im thinking the s70's would be heavier because its larger. 4. Exhaust system- adds power and drops weight. 5. coilovers- better handling and drops weight. That's about 200 pounds, and still have all your creature comforts. good luck