Mike,
That is an interesting question...and the answer depends on your objectives and time frame for achieving them.
Consider it will take several months to build the new pond. Then a period of time to fill it, which could be months or even years. I don't know your locale or fish preferences, but it can easily take another two to three years on top of that to establish a quality predator fishery.
In the meantime, you could be catching fish and improving the existing lake.
The DIY aspect of planning and being part of the construction and establishment of a new pond is not for everyone. It is rewarding, yes, but also fraught with significant risks. Not many have hit it perfect the first time....heck, I'm on number 5 and have not even come close to perfection, but I enjoy trying.
Only you can make that trade-off between current enjoyment of existing pond vs planning and building a new one. Risk assessment should be part of that decision making process, IMHO.
