Hi Cheryl! What a beautiful family you have!! What a blessing a set of boys will be for that estrogen run household!!
Christel's list is great! Great idea on the mattress covers - never did that!
I'm a total preparer and wanted 2 of EVERYTHING although once they got a bit older we realized that one baby liked things more than the other baby (ex: the jumperoo) so we really only needed one.
We used a pack n play next to the bed for the first few months and then had 2 cribs in their rooms. The swings were a LIFE SAVER for us so I would recommend getting 2 of those bad boys. We had 2 bouncers, 2 excersaucers, 1 breast friend that was given to us by a friend and 1 boppy. I agree that you should stock up on diapers as you get coupons. If I would have known how much formula mine were going to drink I would have started buying that really early with coupons too. But - you don't know if they'll need a special formula (if you're going that route) so that can be tricky.
I'd hit up a local twins club rummage sale and stock up! We did and got 2 of everything for really inexpensive!! You could also check Craigslist or your local paper. As you know, most of the things you spend a fortune on you only use up to a certain point so if you can get one second-hand then do it!!
I don't have any experience with placenta previa so I'm no help there.
Congrats on your boys and I hope you make it over here once they arrive!!!