I just bought a 350 and also got a warranty replacement for my 450 and neither had the drilled plug set up.
My return pump on my 450 is the waveline 10000. It's a DC pump running about 2/3 to 3/4 and pretty quiet imo. I run my skimmer off the manifold and still have plenty to spare. It claims to be apex ready but I have not tried hooking it up.
My skimmer is the Red Sea cskim 1800 and no where near quiet. It skims great and I have 0 no3 and po4 most of the time. Price was good enough to help a little on my set ups cash burn rate.
I originally got an Apex gold for my 450 and after a year I can say it is one of my most under utilized pieces of equipment. That's just me though.I was hoping to use it for dosing and some other control functions but it just serves as a monitor on things that can do without. After playing around to set up a dosing schedule, I wound up getting an infusion pump used for IV in hospitals and it works simple and consistantly. Most people swear by Apex, but if I had it to do over on a budget I would skip it.
Just my limited opinions with my limited experience. Good luck and happy reefing.