Cartridge Output Voltage and it Affect on a Turntable with Pre-amp/USB Outputs

I purchased a Pro-ject Debut III / USB turntable some time ago ( what was I thinking) and I wanted to upgrade the turntable so I purchased a new Ortofon 2M Red cartridge. After I put it on the turntable, I noticed some clipping indication through the USB port on my computer. I don't hear the clipping (or I don't think I do) but I would like the output at about 80% to 90% of 0db. The turntable has no attenuation/gain control.

The question I have is the stock cartridge has an output of 4mV and the replacement cartridge has an output of 5.5mV. Is the higher output of the 2M Red causing the clipping? Should I look for a replacement cartridge that has a 4mV or less output (as long as its sufficient output for the turntable's pre-amp)? Or do I get an Audio Interface and adjust the attenuation/gain with that device? 

I'll await the feedback...