Synology's DS118 is high performance, but expensive, single bay NAS.
Synology's DS918+ is a top-performing, but pricey four-bay NAS that could make good use of a 10 GbE port.
Synology's DS218j and DS218play bring good value and performance to two-bay NAS buyers.
Synology's DS418j came close to taking the #1 rank for RAID5 NASes.
Synology's DS1817 provides high capacity and 10 GbE connectivity at a reasonable price.
Updated - Synology's DS1517+ is an attractive choice for a 10GbE capable NAS.
Synology's DS416 and DS416j are both good values in four-bay RAID 5 NASes.
Update - Synology's RT2600ac Router shows the company is serious about pursuing the Wi-Fi router market.
Don't be limited by simple NAS backup options.