Cutting alum on a water jet- What machine to buy

My company is looking to buy a new or used water jet to process, up to 1/2 inch thick aluminum. Most of the parts will be cut out of 3/16 aluminum and sometimes we will use it for .5 inch alum parts and steel parts, but the steel would not be over .25 inch thick.
The table needs to be at least 4 x 8 ft cut area and cuts as fast as possible on the 3/16 thick aluminum.
Do any of you guys know which machine would be the best that would not break the bank but also be robust for everyday use.
Thanks in advance