So the QSC is 300x2 in 4 ohms or 600x1 into 8 ohms. Not a problem. You will only need one amp per sonosub. There are a few dual 8 ohm subs that I know of but they won't handle 1200w (your 2 amps bridged).
Is your budget just for the driver or the entire sonosub? You will spend between $30 and $100 on the sonotube. You will also need a port(s), MDF, dowel rod and terminal plate. What tools do you have? A router and a circle cutting jig is a must for a professional looking sub.
I try to design accurate subs. They should work great for both music and movies.
Programs like WinISD and Unibox will give you a recommended design but most of us tweak it. I like ESB (extended bass shelf) designs. Those are larger enclosures with lower tuning points.
T/S explained There are dozens of other sites like Wikipedia and How Stuff Works that will also explain each parameter. What are good parameters? Depends on your goals. Also you can't look at just one parameter and judge a speaker. When you change one parameter, they all change. It's a very complex relationship. And you should also read about different alignments at DIY Subwoofers dot org.
How big is your room? Do you want reference levels at 20 hz? Do you watch action movies? What type of music will you be playing through it? Answer these and the questions above and we can start to narrow the choices down.
-Robert
