his whole system with a GT240 and 100% utilization of both CPU and GPU with 25% cap aging is only 200W. he could easily go to a 5670 or gt240 with his current system with no problems. In fact, the 8500GT the OP's got in there uses more power than ANY of the cards the OP just asked about. No worries in the upgrade :-)
• PCI Express or PCI Express 2.0-compliant motherboard with one dual-width x16 graphics slot
• Minimum 300Watt or greater system power supply (with a minimum 12V current rating of 18A)
• 1GB of system memory
• CD-ROM drive for software installation
The following are the minimum power requirements using a PSU with a single +12V rail. Also these requirements are for a system containing basic components (unless otherwise noted). The more add in cards and hard drives that a system has, the more amperage draw on the 12v rail.
Geforce GTS 250 - 32A and a 500W PSU minimum
Geforce GT 240 - 35A and a 400W PSU minimum
Geforce GT 220 - 30A and a 350W PSU minimum
Radeon HD 5770 - 34A and a 500W PSU minimum
Radeon HD 5750 - 30A and a 450W PSU minimum
Radeon HD 5670 - 26A and a 400W PSU minimum
Radeon HD 5570 - 24A and a 350W PSU minimum
Radeon HD 5450 - 22A and a 300W PSU minimum
Of course, no doubt manufacturer's are a bit conservative, lest remember that warrantees are based upon these requirements.
Given the published system requirements, the 19 amps on the label, as well as the manufacturer's name on the label, I would risk my investment on that PSU.
Well, seeing as he's running a 8500GT, which calls for min 18A on the 12v rail as well, so the GT240 should be fine. (I didn't notice the low 12V amperage at first). So yeah, the 5670 requires more 12V Amps than that, so sorry that one won't work (my bad on missing those requirements) but the GT240 has the same requirements as the 8500GT.
Edit: well... my researching gave different results than yours I guess... Maybe MSI has different specs. Maybe what I found was not legit. whatever the case, The newer cards DO seem to draw less power than the 8500GT the OP has, but I guess that doesn't mean it would be a good idea:-) Thanks for the research Jack and the correction before I let someone blow their PSU sky-high.
My research still shows the 8500GT power usage as higher than the any of the other cards mentioned in this thread. I'm not sure how they could draw less power and use more amps on the 12v rail. However, best bet is to get a solid 350-400W PSU and not have to worry about it.