before kayaks porked into bass boats and 20-somethings at kayak shops told us over 30" wide was a good thing because we wanted to stand to fish and sit in an upright padded chair, 50 lbs was the norm on 14' kayaks. The speed and glide of these older style kayaks is a joy.
It seems like keeping your 9' boat and finding a good used 12' or 14' to extend your range would be the way to go.
However, if what you want is the easy chair, you may be going the right way.
But there are still ways to handle heavier boats without injuring yourself.
Even my 76-lb 16' tarpon is not tough to single-hand with forethought.
If you have a pickup, a bed extender lets you lift and swing half the boat at a time, and lift only 3' at a time.
A big-wheeled dolly lets you move it a long way by yourself.
Here's my buddy rolling his 100-lb Revo to launch.
If I was sliding that boat off my bed extender, I could put those wheels into the skupper holes, and keep sliding without ever lifting the boat - until I had to lift half the boat to take the wheels out. Conversely, to put it away, could roll it up to my bed extender and slide it right on, finally dropping the wheels when I lifted the last half of the boat onto the bed extender.
At my garage, I back up and slide my 16' Tarpon directly onto a pair of sawhorses.
Next to it, btw, is my used 14' boat, a 39-lb kevlar Kestrel that cost me $950 - this narrow fast boat is not for everyone because what you gain in speed, glide, and being totally wind-proof, you lose in primary (sitting still) stability. It's one of those choices you have to decide you want.