Remember Xbench?
This is a fusion drive.
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This is a hard drive (USB 3.0 Superspeed)
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Is 0.79 MB/sec really appropriate for today's computers?
Anyway-- enough tech talk.
You can say that you don't play games, so you don't need a fancy video card. You can say that you don't do number crunching, so you don't need a fast CPU. You can say that you don't... use photoshop..., so you don't need more RAM than what apple provides.
What you can't really claim is that your computer doesn't need to read or write files, so it's not being held back by vintage technology.
Anyway.. that's my reasoning. It's a primary bottleneck, and an fusion drive or SSD is the best way of rebalancing the system.
Rambler358 probably wants his wife to have no complaints with the new system, and a fusion drive or SSD is a good, cost effective way to make everything just a bit snappier, a bit less creaky--more so than adding ram, or upgrading the CPU, or adding memory.