I would be replacing:
Pentium 4/HT 3GHz
Windows XP Home
Dell 16 inch Trinitron CRT monitor
1GB Dual Channel DDR2 SDRAM
80GB ATA Hard Drive
6x DVD 16x CD/RW combo drive
256MB ATI Radeon X1650 Pro 3D video card
...with no digital-only media files
with this (its closest Dell equivalent):
Pentium D Processor 935 with Dual Core Technology (3.2GHz)
Windows Vista Home Premium
Dell 19 inch SE198WFP Widescreen Flat Panel Monitor
1GB Dual Channel DDR2 SDRAM
320GB SATA Hard Drive (7200 RPM)
16x DVD+/-RW Drive
256MB nVidia Geforce 7300LE TurboCache
...for a total cost of $859 plus taxes... so....
My computer is worth under $1,000 to me.... but its replacement would be far better than what I have now.

Can't say I'd miss it.