If your looking for decent used parts, go to sohfast.com , I'm dealing with them right now. They can get a lot of parts that they don't list, so Its a good idea to talk to them via email for the best prices and products.
as for when you do the rear conversion, its real good idea to buy remanufactured calipers, because you have no idea what condition your donor vehicle was in.
the 4040 valve isn't REQUIRED but is recommended for better braking power.
and also, if you're looking to go with a big brake setup, and if you have some cash, take a look at
http://fastbrakes.com/home/
they have kits for rear disc conversion, where I think you just bolt on some brackets. They provide everything for you, but you're going to pay for it, some of the kits range between 600-1000 dollars, but its good stuff.
I'm pretty sure for the front brakes you can switchover everything from the 90-93 integra, you can buy the knuckles each side for 100 each. I dont remember much about doing the front, so you'll have to do some research.