Like Tshirt has said, don't buy a D2 modem. You want to buy a D3 modem.The cheapest D3 8x4 modems are the DPC3008 and the Zoom 5341j.
The 5341J(Remember the J) is about $80 and the DPC3008 is $69.99 at the time of this posting.
The firmware on the DPC3008 seems to have fixed it's issues. I'm on a Cisco CMTS with this modem that I got a couple days ago and it hasn't dropped once. It just still has poor logs