Is there any way to receive more channels by just changing the CableCARD™ I have?
No. A common misconception is that the CableCARD itself determines whether or not a TV or other retail device can access two-way services like SDV. The reality, however, is that the current CableCARD devices were designed only to access one-way services. As a result, in order to access channels delivered using SDV on a CableCARD-compatible retail device, you need either a Tuning Adapter or a Time Warner Cable digital converter.