Sam, you didn't specify budget. If it's just for hobby ($0 + negative time value), OpenFOAM/ParaView/Salome will solve everything that the big boys can but the UI will make you wish you had a different hobby. There is plenty of academic code out there to get you started.
For most any PDE solver you'll want to invest in the fastest DRAM, not necessarily the hottest CPU. If you want to be really serious about it, the IBM Power architecture will generally outperform Intel by 2x-3x at these kinds of workloads, but it is not for the faint of heart.
Finally, no software will get you very far unless you have deep understanding of the math. Oleg Zikanov's "Essential CFD" is pretty good for the basics.