Water cooling is a fad really for inexperienced pc users, so you should avoid it. I agree that building your own system will give you many more than a few years use before you need to upgrade.
If you buy well and plan for the future with your system you can get more than 10 years out of it. The $3200 sounds too expensive you could build a fantastic system with everything you want and still pay less.
There’s plenty videos available on building pcs to guide you.
Its going to depend on what games you play and plan on playing. Plus what resolution you’ll be playing at. Do you know what resolution your current monitor is?
That is a 4k Gaming rig. The price isn’t too bad considering your GPU (RTX 4090) new is 1600.00 MSRP (but likely higher on the street). It is the top performing GPU currently. If you are not going to be playing at 4K you can probably downgrade your GPU and save some $$.
Looks like they are skipping on the RAM though and 64 Gigs aren’t really needed. 32 Gigs at a higher MT speed would be better…
I’d stay away from that processor (i9) for the time being. Its not top of the line for gaming and there maybe some issues intel needs to work out.
If you want the best Gaming CPU your looking for the Ryzen 7800x3D from AMD.
You should be able to find prebuilt PCs that’ll fit your need. One of the benefits of a prebuilt is the single support source and warranty.