Dell Studio 435mt Video Card Upgrade - Will it work?

Hello everyone, First post here.  =)  I'm looking to upgrade my graphics card after having used the ATI 4800 series card that came with the Studio 435 for a couple years now.  I have done a little research and read a few forum posts here and there and have a bit of an idea, but a few things remain unclear. I guess I'll just ask my question:  Without upgrading or changing my power supply, can I install and use a GeForce GTX 560 or a Radeon HD 6770? Also, if I do need to replace the PSU, can you suggest a model with a good price that would allow me to use one or both of the cards mentioned above? Finally, as an alternative to the first and second question, could anyone say what the best possible graphics card upgrade that doesn't require a PSU change for this system would be? Thank you!

The specks listed by nvidia won't let you use that card in your system, as your PSU does not have it's own 2 x 6 pin power connectors. What you will need to do is, install a ATX type PSU. I use the Corsair CX 600 w PSU in my system, and I have the same size of case as you. See HERE for a PSU, and HERE for your manual, nvidia system specks below,

Thermal and Power Specs:

Two 6-pinSupplementary Power Connectors

Thanks for replying, RobinBredin. I read about the 2 x 6 pin power connectors and it seems that the recommendation you made for the PSU is a good one.  I'll look into getting that one soon.  Thanks! And if anyone knows what the best graphics card upgrade I could get for the Studio 435mt without replacing the PSU and could let me know what it would be, that would awesome too.  I'll probably just buy the new PSU and one of the cards mentioned, but if I can get a good GPU upgrade and save some cash, that's always nice too =)

If you want to keep your PSU, then go for this card HERE, it's the 5670, it will run off a 300w PSU with no power cables.