I own both their dual and quad pcie tuners. The quad is good though runs a little hot for my taste. For me, there is no reception quality difference between the two.
Are you saying that your existing dual tuner produces bad recordings in MC but perfect ones with WinTV?
For signal strength, there is a standalone Hauppauge signal strength utility (displays strength, correctable and uncorrectable error rates). I used this to position my antenna. You run the utility while MC is recording a show on tuner #0. It then displays the real-time signal details. You can go through various channels and get a broad view of your signal quality.
MC has it's own signal strength info but you get more detailed results using Hauppauges own tool alongside MC.