That Vantec PSU is an old design. At best, it will be very inefficient. At worst, it's an overrated piece of junk that will be unstable under load and/or take other parts of your system with it when it croaks.
To mi1ez's short list, I would add Antec and Enermax.
With a 20-pin power connector, that Dell mobo is sufficiently ancient to very likely have the bad capacitor problem that is very well documented online; do a Google search for "bad capacitors."
With a 20-pin connector, also make sure it wasn't one of the proprietary ones that Dell used. In that case, it would look (and fit) the same, but have different pinouts than the standard; should you plug a standard PSU into it, the mobo and/or PSU will smoke, choke, and croak.
I believe PC Power & Cooling makes a Dell-specific replacement.