Looking on ebay, it looks like your estimates are closer than mine on new equipment. I paid $1700 for my FantomX6 more than a year ago and can probably get $1100-1200 for it now. When I was looking to buy, the street price for a new one was $2000 and were going for about $1500 on ebay. That was last year and the Fantom was the latest model. The new G model will decrease the X's value.
But the return on used equipment looks much better. I'll bet an X6 in good condition bought today for $1200 could be sold for almost the same price a year from now.
OTOH, a computer is worth practically nothing after a year's use and used software and sample libraries have no resale value.
If I had to choose, I would drop the hardware, but having both is the best and worst of both worlds. The things I like best about the FantomX are the portability, sounds, midi accuracy, and reliability. Everything ends up the computer for ease of editing and audio tracks. The FantomX has 8 audio tracks but they take forever to load.