I actually own both the Coralife 125 and an Aqueon Sump.
While the Coralife 125 worked fine, it is nothing compared to my Reef Octopus. It made plenty of gunk but the bubbles were not as small as a quality skimmer will make therefore the proteins taken out will not be as good or should I say it won't deep clean as well.
The Proflex Sump however is awesome. Costly to say the least but very convenient and built very well. My current tank requires to many add ons to own one but for a more simple set-up they are perfect.
I agree though you can build one on your own for 1/4 the cost or maybe a little more say 1/3. Plus if you make your own you can make it custom to hold things you want to add later.
BOTTOM LINE
Get a better skimmer if you can afford it, if not this is not the worst but for the same price you can probably get something better.
Aqueon Sumps are fabulous but costly. Saving money by making a sump or Craiglisting it can get save you money and then you can get a better skimmer.
A quality skimmer is to me the most important thing to a reef tank. I didn't always think so but you will see it is and of course good husbandry is a given.