Phenom II x6 1090T vs i7 920 vs Xeon for multithreaded applications

Couldn't find an exact answer to my question so... here's my post:

I need to purchase a computer for my lab (must be through HP) to do computational fluid dynamic simulations. The program I'm using is Ansys Fluent 12 and it is a 100% multi-threaded app (literally to the point where you can specify how many processors you which to use). I'm having a bit of a problem now selecting a computer to buy.

My computer at school is a HP xw6600 workstation with Dual Intel Xeon E5410 processors and 16GB of memory. Now, I just put together a computer at home with an AMD Phenom II x6 1055T and 4GB of memory. Surprisingly enough, the computer at home will solve a simulation in less than half the time it takes for my lab workstation to solve the same simulation... hence the reason for the new lab computer. (need a reason to come to school, right?)

My question is, out of the Phenom II x6 1090T and i7 920, what would you recommend to buy? The price difference between the two computers is only about $200-$300 more for the Intel chip.

Also, would a Xeon setup be THAT much better? The price of a Xeon build almost doubles the price....

Thanks,
Ryan