Z'ha'dum now has internet connectivity! The cable installer showed up at around 1400 hours today, and by approximately 1500 he had the job completed. Comcast had no problem with me providing my own equipment, they just needed the MAC and the serial number for entry into the HFC system's head unit. So now my PC is hooked into the D-Link firewall/router, and the router is patched directly into the cablemodem. The cablemodem needed a better coax connection to work, but once that was fixed it registered on the network just fine. I've already taken it out for a test drive, and all I can say is that I'm absolutely amazed... according to the bandwidth benchmark system at Broadband Reports I am pulling down roughly 3050 kbps and uploading at somewhere around 252 kbps. I'm practically rolling in download bandwidth. Even more amazing is that with the D-Link router/firewall in place I am completely isolated, my PC is well-secured from the Internet -- they can't even ping me. I've run port scans against my IP from multiple servers and every single one of them has turned up empty-handed. It's hard to exploit what you can't see.
It's an understatement to say that I'm lovin' this. I just hope that the 250-or-so kbps upload is enough for me to work remotely (VNC and ITO can be a real pig sometimes) and that this network doesn't get too badly choked up during peak hours.
Still, even if I get cut to half my peak bandwidth during "rush hour" on the system I'm still pulling down a good speed. I'm not swayed completely away from DSL, but this cablemodem has made a good impression so far.