There is no such thing as a 2.5M profile. There is only 1.5M and 3M, thus you are a 3M profile that will give you the highest possible speed your modem/line can handle. Your line attenuation is so high that its probably why your upstream maxes out at 640k instead of 800k.
shmore2,
Your attenuation is pretty high that's why you are getting 5 SNR, if it were lower, say in the thirties you would be getting around 15 to 20 SNR so don't listen to cybersnow.
