Doom 3 won't play, but VPC will probably work just fine as long as you (a) avoid games, and (b) use Win2K instead of WinXP if at all possible.
Obviously, if you're big into games, you won't be happy with any Mac compared to any $1000 PC, but I think you'll find that, aside from games, the Mac is a better overall value, and I'm certain that your wife will truly appreciate the clean lines of the iMac.
If you're ordering online, I recommend getting Bluetooth built-in as part of the $100 BT/keyboard/mouse deal. Then it'll look even cleaner - no wires in front.