I get you about wanting to do everything at once. Also, I have the convenience of just driving down the road to a well-stocked place, where I can browse. I usually don't mind visiting that place multiple times
Now, about your question.
What you don't want to do is use any regular (double braided) rope for an all-rope halyard. The stretch is definitely going to make it perform worse than the rope/wire combo.
The alternative is a combo using Dyneema (Amsteel etc.) in place of the wire. That gives you the same low stretch and is lighter (always a good thing). However, to do that right takes a bit more time and educating yourself on how to splice rope to Dyneema. There are some ropes that are covered Dyneema, which you could use instead - you'd be paying extra for the "tail", but they would be usable as a single piece.
You would select them based on the lowest diameter that still gives you acceptable stretch (breaking strength as such is generally never an issue, but higher strength means less stretch as rope stretches by a known percentage when you load it to about breaking strength an proportionally less when you stay below that value). They would probably be quite thin (1/8" ?) which is good for saving weight aloft, but may give you handling issues.
For the main, you normally raise it with the boom free until you get full hoist, then pull the boom down to the stop to get tension on the luff. That's how it works on my DS1. If your's is different, and you need to set the tension by pulling on the halyard, smaller diameter rope can be inconvenient (also need to make sure it's gripped well in your cleats - pure Amsteel tends to be too slippery that's why it's used in a combo).
For the jib halyard you may eventually add some tensioner (some way to get 2:1 or 3:1 purchase, so that you can easily adjust the tension on the luff according to the wind conditions).
That's also something you may want to plan out in some detail - that was the reason for my suggestion not to rush into replacing a working setup w/ wire-rope combo.