I spent 55k OTD on my 242 Baja Islander (original list was $69,xxx) including trailer, taxes blah blah blah. I bought it in mid-August (end of boating season) of last year as an 05 model.
I primarily use the boat for lake duty and have taken it to the Outbanks in NC once so far. Since your not sure whether or not your going to get full use out of the cabin I would say this little family bowrider meets your requirments with one exception. You say you want to go 70mph. My best GPS as of last week is 64mph with the 496MAG non-HO. I picked up an extra 2mph once my hourmeter passed 30 hours. The bowrider is a blast because I can take all my friends and family out. A couple of weekends ago I had 6 adults and 3 little nieces onboard, couldn't have done that with a Cabin. The boat is surprisingly spacious. I doubt you would see 70mph if you went with the HO, but you would be in the solid mid60's for sure.
The other thing I like about this boat is the 24degree deadrise. Once I get more experience under my belt (only on my 2nd season of boating) I plan on taking her out in the Atlantic to experience what so many other members of OSO talk about.
Last thing. If you new to boating I strongly suggest taking a US Coast Guard Auxillary Boating Safety Class. Best thing I ever did and a real eye opener.
Good luck with your purchase!