Are these upgrades compatible with the XPS 8300? I am aware that my XPS came with a 460w PSU, but I want to get one that matches the minimum requirements for the Radeon 6870 (just to be on the safe side).
Note: I have also read that the 460w Dell PSU will provide more than enough power for the Radeon 6870, even though 500 watts are recommended. I'm still not sure about this, and want your opinions: Do I really need to upgrade my PSU in order for the Radeon 6870 to work properly?
I have read someone, who does seem to know what he is talking about, say that Dell PSUs can provide more than they claim (much like branded high quality units do).
It is also possible to run a system with a 6870 on a high quality ~450W PSU.
A 6870 needs two 6pin PEG PCIe connectors. So if the Dell unit doesn't have those (and it doesn't have enough 4pin peripheral connectors to use adapters, which would probably not be a good idea with a unit of unknown quality) then you will have to buy a new PSU.
Neither the eXtreme Power Plus nor the GX (original 80Plus - the newer 80Plus Bronze series is more acceptable) series are worth buying if it can be avoided.