not that I know of. limitations in how the phone system works prevent the modem to get any faster.
ISDN however uses the same frequencies that a modem (and normal conversations) does over the phone line, only it's in digital form (no conversion necessary at either end). because of it's different method of transmitting data, it can hit the speeds you want, but you're not looking for an ISDN solution.
I'm out of range for any sort of high speed internet save for satellite. because of that, I tried asking my phone company about ISDN (it has a longer range than their ADSL), and they said they were fazing out ISDN completely, so we couldn't get it. it's a shame!