Fastest GPU with no external power required?

[Columbo]

I'm looking to drop a GPU in an old S775 office machine.

What the fastest card available that doesn't require an external 6 pin power connection?

It will be playing some older games but nothing too demanding and at 1280 x 800 res.

 

[Columbo]

Cheers lads, I presume the GDDR5 version is significantly faster than the GDDR3 model?

 

[Columbo]

cant you use a molex(x2?) to 6 pin from the psu to use a better card ?

No, as its a Fujistu Siemens Office machine there are zero spare cables on the PSU and its only a 300W with 12a on the single 12v rail.

It does have an E8500 in there though, 1tb hard drive and 4gb ram.

As it's only for my daughter to plug into her TV to she if she likes PC gaming, rather than the usual console stuff I don't really want to drop a wedge of cash on something that maybe a 'fad'.