Plumbing

I'm ordering a Reeflo dart hybrid pump from Marinedepot.com (once they are in stock) to replace the two mag 12 pumps that I currently use on my freshwater 500 gallon tank. (I know is FW and this is a SW site, sorry) My question is can I run 1 1/2" plumbing on the inlet side of the pump instead of the 2"? The reason I ask is the cost of the 2" bulkheads, ball valves, and unions is way more than the 1 1/2" parts. Is using 1 1/2" parts going to be ok or should I just bite the ...