Questions about the Precision 7920 Rack

I'm considering a 7920 rack but trying to keep my costs down as this is personal.  Appreciate any input:

1. I have a stack of 12TB SAS hard drive from Dell already so don't want to keep buying stuff.  If I get the basic SATA drive and just that will I be missing anything in the system that would come with a SAS drive?

2. I can't order the PERC controller I want as then it wants me to get more hard drives and then any configuration for raid wants 4 or more drives.  If I buy the PERC card after the fact will again I be missing something that normally comes in the system?

3. Theme here.  The hard drives again.  If I don't get hard drives are sleds provided or just for the hard drives you order?

4. Not sure I'm replacing it, but will the pull out rack rails for my R5500 work with this?

5. Anyone know the sound level of this unit compared to the R5500?

6. Unrelated to the 7920 but if known, anyone know the sound levels of the 3930 rack?

Thanks.

JR