I don't know the prices you're looking at but I swear by my Grizzly 3 hp cyclone and the ductwork is not sealed completely I hear some of my end caps whistling while I work. One day I'll seal them but I just use it as is and no problems.
The only time it seems not perfect is if I leave other blast gates open and I'm using my SCMS, it still pulls enough so the cloud doesn't leave my homemade hood, but if it is the only gate open there's next to nothing left basically some that bounces of the saw's fence.
I know I've read posts by someone on here that says good things about Grizzly's 2 hp cyclone as well, but I think they said they would good for the 3 hp if they had the room for it.
My shop is similar @ 25' x 25'.
Anyway as you can tell I'm a fan of the Grizzly cyclone.