I think your decision to replace in "stages" is a smart move.
One thing I'd warn about is your next set of upgrades. I don't know what your lighting design is so I can't really make recommendations as to which way to go next. I think the idea of replacing one set is smart, in order to raise funds for the next two sets of upgrades.
The throw is quite a bit. Are you hitting zones or just doing a general wash in a single static color now? I'm jus not sure if the Brick can throw that far with the more narrow-beam you've been accustomed to. I'm wondering if a more "like for like" replacement might be more suitable. But, with replacing 8 cheap Parcans(I mean, by comparison, not that you're being cheap) and dimmer packs with LED cans, it's a bit costlier going with 8 LED cans over what you're looking to go with.
You're going to have a LOT of fun with your new RGB options though.