anyone know anything about the following DJs?

So I am having my reception at Crest Hollow and they gave me this packet of suggestions for vendors. Of all the talk abou DJs I dont think I have heard the following companies mentioned. Does anyone know anything about them?

-Ej the DJ
-Hart to Hart
-The Entertainment Group
-New York's Ultimate Entertainment
-Elegancia Entertainment

Also, does anyone know how easy it is to use a non-preferred vendor somewhere with regards to liabitlity insurance, is that something easy and standard to make sure your vendor has or is it a pain?

Thanks in advance.