Well, there ya go. If you want a faster connection you need the faster account type. They aren't slow, you just have to pay for the account/speed that you want.
For reference, this is the account that I have.
I have a 25Mb+ connection and I never have issues maxing out. You sure you are using the right amount of threads? Their bandwidth is capped per thread. You should be running about 20 threads/connections if you want to max out a 25Mb connection.
Congrats! Yeah, when comparing by price point, the Onkyo will have more features, but in terms of sound quality, the Denon wins hands down. I own a 4308Ci and it's great. I have an Onkyo in my office and I haven't been too thrilled with it.