i use a submerged mag 7 in the return section of the sump (75 gal.) after the skimmer and the bubble traps. a ball valve helps control the flow rate and return the chilled water to the first section where the overflow pipes come in. eheim green tubing was chosen for easy plumbing. the whole set up only took me 20 mins.
some had suggested that this route may not be as efficient as if the chilled water were to return to the display but like i said... easy plumbing and 20 mins set up. plus less connections/t-ing off less chance of leaks. i had this set up for over 3 years and it had served me well.
consider where you're planning to put the chiller. it needs breathing/venting room preferably in a different room/area than the tank or the sump. it produces quite a bit of heat. under the stand is not ideal. also the further away, the more powerful pump you'll need (bigger pump = more heat the chiller has to dissipate)..... plus pushing water back up the display tank includes more vertical head loss.
am i just confusing you ?
btw what size tank/set up? what size chiller?