Sales people lie. 64 Kbps sounds like a pretty lousy cable connection speed in the first place. Considering that a so so dialup modem is 26 kbps have them explain how 6 or 7 can be good for a cable hookup? Do an extended ping to your default gateway with packets loaded to 1500 bytes. If packets are not being lost, then it is not affecting speed.

Cable hookups are a shared medium and this is the big difference between CABLE and DSL. This means that your actual useable bandwidth is largely determined by what other people on the network are doing. Hence DSL comes with a CIR (committed information rate) as far as I know, cable doesn't. You might try testing your download speed at odd times and see if it changes substantially. You've seen the commercials on TV where the parents are assigning computer time to the kids at 2-4 am and such (very funny), but this is what cable is all about. If you're lucky and no body else is using it you get great bandwidth, if you're not and lots of people are downloading music and video files, you're screwed.

Also, port blocking does not affect speed or bandwidth. Normally it limits your usability so you can't run web servers and such. Do they tell you what ports they block? I doubt that they are too worried about your security.

Network speeds are usually measured in BITS per second. If your 6 or 7 kbs is KiloBYTES per second, then it's right on. 6 * 8 = 48, 7 * 8 = 56.

That is slow for cable, considering I'd pull that in sometimes on dial-up! (The trick is to find an ISP where you're not in their main area. Fewer people will use them, and you'll get better speed. Only works well if they have a local number for you ;-))