Excel 2007 with 1.9 gb ram too slow, need faster options

Any help on ways to make my life easier with better computer processor.

I work with up to 500k rows in XL with formulas.

What is the fastest processor and/or computer out there?

Could you show the formulas and the criteria?

=if(q2=0,0,(m2-q2)/(q2)*100)
{=100*($i2/max(if($b2=$b$2:$b$21777,$i$2:$i$21777)))}