The CC7870 is nothing more than an older design (it was around in the mid-70s) of a splitter in an unshielded plastic outdoor box. A $6 CATV Ideal splitter from the hardware store will usually do a better job. It doesn't isolate even as well as a common splitter. Save your money.
http://www.winegard.com/kbase/kb_tip...hp?tip_num=289
I tested several of them against our two port splitter a few years back and found that their insertion loss really started dropping off above 600 MHz. Port-to-port isolation was at leas 10 dB lower than was our splitter.
You still haven't solved the issue of no reliable VHF reception with your Sony. Hopefully the 5-element antenna will do the job.