Two trains of thought here. The first being, 19# injectors should be fine for your setup, and buying 24# injectors will also require you to buy a 24# MAFS.
However, since you have to spend money on injectors, why not go ahead and buy the ones that you will need as opposed to buying 19s now and 24s later?
That was what I ran into, when I was building my engine I knew I was eventually going to use nitrous and eventually build a stronger motor. So when it came to injectors I found a good deal on 24s and went ahead and got them. With my current setup, I could easily get away with 19s. But I figured it made no sense to spend money on 19s now, only to have to spend more money on 24s in the future. 24s won't hurt you as long as you have a 24# MAFS and tune the car accordingly.