BTW, the cloudy water will go away as the tank cycles...just keep a good eye on your ammonia and nitrite levels...with the biospira they're supposed to go down in around 48 hours.
I'd keep testing for ammonia and do water changes sufficient to keep it below 1 ppm. Be a shame to have those nice Oscars get ammonia burns...
The cloudiness may or may not have anything to do with the cycle. Besides the nitrifying bacteria, there are a lot of other normal microorganisms that live in our tanks. It takes their populations a while to stabilize, too.
I'd ignore the cloudiness and keep track of ammonia and nitrites via testing. Those are what you should worry about.
BTW, beautiful tank. You're really doing this right...
Canisters often have a minimum height that they must be below the tank, can't be even with or above, so often that will cause a problem with a canister on a sump, but check the particular canister. The one you are looking at may be fine sitting on the same level as the sump.
I have a monster DIY wet-dry on my 135, and love it. I made it out of a 50g rigid plastic "truck bed" box for the sump, and two identical filter units, each one made of a pair of stacked Rubbermaid containers. I think the ones that hold the Bio-balls are about 18 gallons, and sitting on top is a shallower one with a 4"-thick layer of foam (this takes care of the small particles mentioned upthread). I love those Rubbermaids, because for any given footprint, you can get a variety of depths, and they stack nicely. I poked a zillion tiny holes in shallow ones that hold the foam (just me, my Dremel with a tiny bit, and an episode of Grey's Anatomy). I cut a big hole in the bottoms of the bio-ball containers and replaced it with eggcrate.
It works great, and I run one overflow to each unit. Having two indentical units means I can clean them on alternate weekends--just take them out and give them a good blast with the garden hose--without worrying that I'm crashing my biofilter.
I've seen canisters run as if the were return pumps with the intake in sump and outflow into the main tank. I've seen an XP3 used in particular and the guy used a powerhead in the sump plumbed into the XP3's intake to get it to work more reliably with the intake below the unit. Or you could just rug up a modular style canister filter inline with the return, like an ocean clear or pentair.