Dell Optiplex 755 Upgrade?

It seems your Dell has a 305 watt PSU. The GT 730 requires 300w PSU - minimum. The PSUs including in these machines are cheap and often cannot output the wattage they claim to output. Some can even explode under load, frying everything in your PC. I'd say it outputs 250w - max.

I'd get a new PSU before the GPU. While your PSU just meets the required wattage, your PC can shut down or freeze becuase of low power. Fortunately, the PSU in your PC is not propietary. You can fit any standard ATX PSU in it. I'd recommend the EVGA W1 500W or 430w - http://www.newegg.com/Product/Product.aspx?Item=N82E16817438015&cm_re=evga_430-_-17-438-015-_-Product

There is also a 500w option too. Just don't cheap out and get something crappy like a non-branded PSU. Don't get the Corsair CX series though.

Hope I helped.
 

I Agree but i have heard storys about cards that require 400min running off of dell 250 watts
I would kinda want to here word from someone else before haveing to buy a powersupply to.
 


While it may be possible, I don't recommend it. Like I said, doing that can be a danger to yourself and others around you.

It's just not worth the risk. Buy a quality unit, and you'll have room to upgrade later on. Don't, and regret it deeply after your system goes up in flames.