CM2000???

Well techinally maybe possible to get over 1000Mpbs, remember that just a overhead bonus. Any wired LAN cable connection is still limited by the 1000Mpbs connection rate. So some wired adapter may see over 1000Mpbs on the wired and some like me, maybe see under under 1000Mpbs, I've seen 950 on my Mac Book Pro and Windows 7 PC with 1000Mpbs wired adapters. Also CPU of PCs and laptops will play a roll as well. I presume if you have a tri or more core CPU, then you are well capable of seeing over 900Mpbs and depending upon the wired adapter and quality of the LAN cable, maybe see 1000Mpbs or maybe just over. Also ISP signal line services and cable coax quality will play a roll as well. Other ISP users on the same ISP service line as well will be a factor. 

Techinally if you had a 2.5Gb wired adapter, CPU capable of handling that speed, and your ISP services and allowed for 2.5Gb speeds, then I would presume you should see 2.5Gb speeds running thru the CM2000 modem. 

Were just beginning to see higher speeds on the WAN side above 2.5Gb on modem and router hardware. There will be other factors that will contribute to the consumer seeing these speeds in the future. Were still waiting on the LAN side to see these connection rates. Were still stuck with 1000Mpbs at the consumer level. Just like it was when we were at 100Mpbs and finally got 1000Mpbs. Took about 10 years or so for this to happen at the consumer level. Now were again waiting for the next step on the LAN side. 

So if you get over 1000Mpbs on the LAN side to the WAN then thats good, if your not, then keep in mind about the 1000Mpbs LAN connection limitation. I would not always expect to see over 1000Mbps all the time.