The basic chassis looks good, but I would look for a 7200RPM drive.
I would also purchase aftermarket memory, as HP laptop memory is notoriously slow.
The main advantage of x64 bits is to add memory, so I do not know how much advantage x64 will give you over x32, but it should give some.
Also consider adding 4GB ReadyBoost RAM (a fast flash card).
And I do not know your budget, but Dell makes workstations that handle more than 4GB of RAM, which is where the real advantage of x64 is found.
http://www.dell.com/content/products/productdetails.aspx/workstation-precision-m6400?c=us&l=en&s=bsd&cs=04&~oid=us~en~4~workstation-precision-m6400_anav2~~
I hope that helps.
Norman
