Newegg.com - SAPPHIRE 100166L Radeon X1650XT 256MB 128-bit GDDR3 PCI Express x16 HDCP Video Card - Retail: $114.99
Well, better than integrated graphics, I guess. WoW occasionally reported framerates of 2 (yes, two frames per second -- while flying into Shattrath City) on the Mac Mini-in-law. Haven't yet measured on the integrated graphics white box, but I could use an upgrade.
Update 6/24: Since this post, the card has gotten a $20 rebate, making it $94.99, then hit $149.99 for a while, $129.99 with rebate on the last day that rebate was valid, and is now $104.99, $84.99 with the new rebate offer. Wacky.
Unless I talk myself into an 8500 GT now, I'm getting it. Hope I don't need DX10 soon.