The DV6 does show dedicated video cards as an option, meaning it probably has an MXM 3.0 slot in it for that purpose. Contact HP and find out what models are available. They should include the necessary heat sinks and hardware to install if you order from HP.
HP shows these as available for the DV6 when ordering new:
NVIDIA(R) GeForce(R) GT 630M Graphics with 1GB GDDR3 memory [HDMI, VGA]
NVIDIA(R) GeForce(R) GT 650M Graphics with 1GB GDDR5 memory [HDMI, VGA]
NVIDIA(R) GeForce(R) GT 650M Graphics with 2GB GDDR5 memory [HDMI, VGA]
I would recommend the 650 1gb. You are never going to use 2Gb for the 650, it wouldnt be worth the investment.