Planning for an asym spinnaker, I'm surely going to add the sprit. I don't like going halfway. I also would think about a symmetrical spin secondarily. The other thought is that a second set of winches at the back quarter would provide an option for genoa sheets when single handed. But the primaries are bigger winches for a reason, and I'm not sure I could get away with using the smaller ones for genoa sheets. Perhaps in light winds ....
Going with a sprit is a good move, just be sure you have or also install a true spinnaker halyard, namely a halyard positioned off a crane in front of the forestay. That way it wont hang up when you jibe your chute in front of the forestay.
If you add a sprit you now also have the option to consider a larger spinnaker as you in effect increase the size of your "J". Of course a larger spinnaker provides more power... but becomes harder to handle. Using a sprit means you might want to bring a sailmaker into your decision and dont buy something off the rack.
IMHO if I was starting from scratch for a spinnaker, since I find the spinnaker use most important for broad reaching and running, I would go with a symmetrical as they are both more effective and more manageable for deep sailing. Most every time I end up sailing deep with my cruising chute, and deep is where you really need the spinnaker, one second of inattention and it ends up wrapped on the forestay which is a bear to get undone. In some forty years, I never wrapped a symmetrical chute...
Asyms have become de rigueur for racing boats because they fly them off big spirits which allow the sail to be twice the size of a standard symmetric and more powerful, although many racers keep a symmetric for circumstances where they need to sail deep.
For a cruising sailboat, I find a symmetric more useful and effective, and far less trouble to fly, than a cruising chute. While a symmetric does take more setup to fly, my practice was to leave the spinnaker and pole lines permanently run, hanging the sheet ends in coils off the stern rail. So hoisting the sail only required clipping the sail on and raising the pole. I think the popularity of the cruising chute is largely due to an unreasoned fear of the apparent complexity of the symmetric.
Being experienced with all forms of these spinnaker alternatives, for a cruising boat, I would vote for a symmetric hands down.