Very timely question, Dr. Bill as I am about to "take the plunge" into UW videography myself and am looking at that very model---I live/work as a Dive Instructor in Thailand, so may purchase locally (Singapore has very good prices) but the housings are all better/cheaper back home (I'm from the OC, not far at all from Catalina--many good dive memories!) and Top Dawg seems to be the "one" for the job, no..?
I need compact, durable, and moderately priced and the Top Dawgs are ideal in those respects...as soon as I get started I will give you my feedback, but as I am a "newbie" with regard to UW Video (but have years of photo experience going back to Nikonos IV and V) I may not be able to give you any direct comparison to HC-3 or other models....but from what I have read the HC-7 should be a "vast improvement" over the HC-3...
If you have specific suggestions as to pricing in the USA for the HC-7 (B & H seems very competitive, and they generally do NOT sell grey market items), and housing ideas, please PM me directly, as I know you have infinitely more knowledge and experience than I in this area.
Also have questions/concerns about lighting : necessary, or just wasted $$ in clear tropical waters? May do wrecks with this video so I am thinking will be useful for those if nothing else!
Best,
Harley