Want to upgrade Dell XPS 8300

[boilermakerloc7]

Please be kind I am a noob. I want to update my graphics for my son so he can play his games.
I have an old dell xps 8300
intel i5-2300 quad core
and an amd radeon hd 6450 graphics and a pci express x16 interface. What would I need to upgrade for not a ton of money or would I be better off with new computer?

 

[popatim]

Do you have a budget for this and what power supply do you have in the old dell?

 

[boilermakerloc7]

It is the original power supply. 460w. Would like to stay below $400

 

[Kisianik]

GTX 960 will work with existing PSU. 460 watt Dell PSU is OK for video cards with up to 225 watt TDP.

 

[boilermakerloc7]

So an EVGA-GeForce GTX 960 will work even with the old PCI Express X16 and old psu

 

[Kisianik]

So an EVGA-GeForce GTX 960 will work even with the old PCI Express X16 and old psu

I prefer MSI based cards or their software and quality, I have 2 MSI cards, GTX 550TI OC, the coolest (temp) card on the market at the time of production, right now my reserve card, and MSI GTX 660, working well for the past few years.
I have nothing against EVGA, however, I am trying to help one user with XPS 8500 and EVGA GTX 960 problem with PC crashes, so can not recommend EVGA 9** series for now, until issue resolves. And, I seen confirmation on YouTube about XPS 8*** series and MSI GTX 960 working well, so go figure it.
So I would recommend any of those http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007709%20600537575&IsNodeId=1&Description=msi%20gtx%20960&bop=And&Order=RATING&PageSize=30