DGPS were do you get it from and with what?

I don't think many recreational boats are using DGPS, mainly because regular GPS, especially with WAAS corrections, is good enough. One unit I do see sometimes on yachts is the Furuno GP37 GPS/DGPS.

DGPS predates SBAS (WAAS/EGNOS/MSAS) and requires a separate antenna & receiver, whilst SBAS (WAAS/EGNOS/MSAS) can use the same antenna as the GPS itself. DGPS only works in the vicinity of a DGPS ground station, WAAS has US coverage whilst EGNOS covers Europe and MSAS covers Japan.

I'd say its clear from the above why most new recreational GPS receivers use SBAS.

http://en.wikipedia.org/wiki/GNSS_Augmentation#Satellite_Based_Augmentation_System
http://en.wikipedia.org/wiki/Differential_GPS

I have a Magellan DBR-IV (OEM: CSI Wireless SBA-1) that receives differential corrections from the land-based network and feeds the correction data to a Garmin GPS 36. Sailing on the Chesapeake, we have a land-based station well within receiving range. I can't remember that last time I saw another differential receiver in use on a boat.

I have never compared it against a set using WAAS to see if there is a measurable difference. I am quite interested in this now because, thanks to Ben's articles, I am interested in the Vesper XB-8000.

As the name suggests, WAAS is a wide-area augmentation system.

Differential GPS signals tend to come from local ground stations, and they cover local areas. This allows for greater accuracy than in a wide-area augmentation.

With real-time differential signals, the position accuracy can be measured in centimeters, while with WAAS the accuracy is still measured in meters.

In most instances of navigating a boat, an accuracy of a meter or two is quite sufficient, so WAAS is able to satisfy the maritime navigators need for precision.

I have a North star 952 which has both WAAS and DGPS. They both seem to have the same accuracy.