Dave I would also recommend that you get the Navionics add on charts. The charts that come in the HDS are inaccurate in the Buzzards Bay area and lack detail too. I posted images here last year as examples, but deleted them online. (One of them showed 5-12 foot depths in the middle of the main ship channel entering Buzzards Bay.)

I used the HDS-7 last year without the radar overlay on charts, and it was still great. The side-by-side display worked fine.