Went -1 front, +2 rear on my 03 600 and I love it. Alot of difference, you'll like it.
Any sprockets will work, if you have a Cycle Gear near you, they are very helpful and treat customers well.
If you can, go with a chain/sprocket kit, which will include a new chain and sprockets that are the same size, i.e. 520 or 525.
Get it local or online, here are a few online places off the top of my head that may have them.
03' GSXR 600
01' GSXR 1000