The 1U servers are very loud. But a 4U or tower server will be fairly quiet, and have the bonus ability to hold more disks. A must for VM's, disk contention on spinning disks gets pretty high after your 2nd VM.
Depends on workload of course, but for most VMs they read a lot more than they write so an SSD can handle quite a few before you notice any IO-related latency (3-4 small web-apps, 1-2 medium, 1 database VM).
The OP also put his two drives into RAID 1 so they won't get any benefit of having two drives.
I use mdadm's RAID 10 on 2 drives for redundancy and speed.
"In mdadm, the RAID10 level creates a single complex software RAID that combines features of both RAID 0 (striping) and RAID 1 (mirroring). Multiple copies of all data blocks are arranged on multiple drives following a striping discipline." http://doc.opensuse.org/products/draft/SLES/SLES-storage_sd_...
You do have more chances for the spindles to be near your data (especially with >2 drives in the array), which can slightly reduce average latency, but that isn't as large an effect.
I'm expecting to cache my VM disks in RAM completely while I do my experiments.