What amp to run Subs?

Hey Guys, I recently got 2 Renkus Heinz single 18 inch sub bins. They run at 500wrms. I want to run them with 2 Double 15 Yorkville speakers i also have. I have an amp to run the double 15s. Ive been told to run the subs efficiently i need to run a cross over unit and get a amp with good cooling and ample power. I was looking at this amp http://www.trademe.co.nz/Music-instruments/PA-pro-audio-DJ-equipment/Live-power-amplifiers/auction-246779646.htm as it has high and low pass filters i could possibly set it up with out a cross over unit?

Ive never run sub bins before so any help or any links you could post would be awesome. I want to spend 1200-1500 if possible for 2nd hand gear.

Thanks

Ben

best to run seperate amp for your tops and subs ...the subs suck alot of power when cranking and best you run it all thru a good crossover...make sure your amp has plenty of headroom ie its a bit gruntier than the spkrs ...obvioulsy dont play it full stoke but it will sound alot better if you can power the subs at 3/4 volume on amp as you wont start clipping ...which is not good for spkrs .....most amps are pretty good these days i run QSC

You are correct on your thinking with an amp with in-built lowpass..