So sad to hear about your cat.
My very loved cat also died from heart failure five months ago today. He was about seventeen. I didn't intend to get another cat for a while, but much sooner than planned, I did; a rescue of around twelve months.
He doesn't replace my cat, who I still miss, but he is a great little chap in his own right, and for me, it has made the loss easier to bear. On the other hand, I don't have another cat whose nose might have been put out of joint. I found some of the of rescue centres incredibly insensitive and rigid. I rescued mine from some students who had taken him in as a stray but couldn't keep him. They loved him to bits and I get frequent emails from them asking for updates.
Good luck with your decision.