Deep and philosophical thoughts (should that be Phylosophical?)
What do you want out of a boat? From your descriptions of your cruises it appears that Cal is everything you want, she is fast, comfortable and moored where you can make use of her on rivers and at sea (and the mooring could be changed anyway).
You two are not going to give up boating, you've hired, looked around for a boat, settled on Cal, so she will be replaced,with what? Will the extra money buy you the boat you want? Would it be better than Cal?
We are selling Ripple (in the medium term) as she is no longer "fit for purpose". I bought her when I was single and could canal bash and maintain to my hearts content. Now married and mortgaged she is stuck on the Severn and it's feeder waterways and both cost and my work on her are becoming an albatross. She has narrowed our boating horizons (if you'll pardon the pun) and we want to broaden them again.
It's alright to be tempted, but money isn't everything, to trade Cal in and then buy a less satisfactory boat on the proceeds would not be a good move.
As an example, we went to look at a Wilderness Beaver recently, if you read the thread you will see I thought it was overpriced. When I saw another one, newer, in better condition, with a trailer, for 2k less, I KNEW it was overpriced (we didn't buy that one either, a small issue with the house got in the way). But the owner was selling two boats. They'd had the Beaver for ten years, and always longed for a narrow boat. They'd bought the NB, and found that, although it had more room, it "wasn't the same" and had both boats for sale. One would sell first and they would keep the other. Given the prices (22k for a good 38 foot nb) I'm sure they'd loaded the odds in favour of keeping the beaver. You might find yourself taking the money, buying another boat and wishing you hadn't.
Hope that helps