Is there a better motherboard for a hp dc7700 sff

Well, here's a list of Mini ITX Intel Mobos, that might suit your purpose, depending on the design restrictions of that Case by HP.
I know what your board looks like, size wise that why the Mini ITX Mobos would be compatible, the only difference is that Cutout, you'd need to see what is fixed there and whether or not it interferes with any overlying component on the mobo.
The other hitch is the backplate for the IO Panel, that whole section is the other way round.
Basically what you need if the Size and Hole layout for the Mini ITX on a Paper and then check is with your case.