Hi
Both models should be within your budget, just contact some re-sellers to get some quotes.
Personally I would recommend the SFF model with SAS drives. You don’t want end up with lots of TBs of storage, but low IO performance.
You could go with 600GB 10k SAS drives and some RAID10 sets. This should be fine for the start. The array can be extended via additional D2700 SAS shelves.
The controllers are active/active yes, but a vDisk is always "owned" by a single controller. Each controller got 4 iSCSI ports what results in 8 ports in total. You can spread the vDisks across both controllers, so that each controller owns 50% of your vDisks. This enables you to leverage all 8 ports but always 4 per vDisks.
Regards
Patrick