HSF
HSF+ (it's a newer version)
You can chose the version desired during the installation (most go for HSF+).
As per adding additional drives the MP, it has 4x HDD bays. It has 2x optical bays (base models ship with a single optical drive, leaving the second empty). If this is the case, you can physically squeeze a pair of 3.5" HDD's in, or 4x 2.5" HDDs (or SSD's).
For ports to connect it to, you have a few options.
1. Built into the system = 2x ODD_SATA ports. These will work with OS X HDDs for both boot or non boot. But not with Windows.
2. Optional cards. You can use an inexpensive eSATA/SATA card, but most won't boot OS X (save one eSATA unit by Highpoint that goes for $229USD). Includes Fake RAID controllers, as they're nothing more than SATA cards with drivers that allow RAID operation (and in some cases, parity array levels that shouldn't be used at all due to the lack of an NVRAM solution for the write hole issue).
Past that, you get into Host Bus Adapters (HBA's) or RAID cards. Not cheap, but you can get far more ports using these. You'd also need external enclosures to use them, which aren't cheap either.
If you're sticking with OS X, you can place the SSD in the optical bay (OS X only), even accompany it with a mechanical for backups. Then have all 4x HDD bays for RAID use (or RAID + backup disk/s).
Windows will change matters, as you'd need to either run it off an HDD bay, or from a SATA card to stuff it in the empty optical bay along with the SSD. You can get a card that works for under $25USD (based on the SIL3132 chip).
