WatchGuard is making interesting use of lower cost components for its firewall\/VPN appliances that can be enhanced to include other security functions.With the introduction of Firebox X, the company is selling a single hardware platform that can be upgraded in four discrete steps to form different Firebox X models: the 500, 700, 1000 and 2500. The main difference from one to the next is higher throughput. Apparently, processors and memory are cheap enough now that it's economical to ship unused capacity in the hopes that customers will pay later to turn it on.But the device offers other options. For instance, the hardware comes fitted with six Ethernet ports, but only three are turned on with the base version of each model. Customers can turn on as many as they like for a license fee, and each is partitioned from the other so it has its own firewall rules.Firebox X also includes a range of security options that customers can buy as they wish, with the features already loaded on the devices and being turned on by a license key. These include Web and spam filtering, anti-virus software and signature-based intrusion detection. WatchGuard also provides desktop anti-virus software and a vulnerability assessment service to customers.The box also comes with a hard-drive bay that customers can use as a place to quarantine suspicious files that are caught by the firewall, which performs both stateful packet inspection and application-layer security.WatchGuard assumes businesses want flexible, customizable gear that can grow without having to swap in new hardware. Customers pay a premium for this option, though; it costs more to buy a low-end Firebox X and upgrade it to a higher end box than it costs to buy the higher end device in the first place.Firebox X base prices range from $1,900 to $5,000.