Due to a needed performance increase I bought a DS710+ and compared performance between the 2 (CS407 vs DS710+).
Harddisk and RAID configuration:
CS407: RAID 5 with 3 Western Digital WD5000AAKS 500GB
DS710: Synology Hybrid RAID (SHR) with 2 Western Digital WD2002FYPS 2TB
For both Synology NAS DSM version 3 .0-1354 was in use – configuration of the 2 was basically comparable (SMB only, NFS, Media Server)
On client side I used a Windows 7 Ultimate 64bit with an Intel 80GB SSD.
Here are the results: