So i could/should go for the dc6000 (1585 gph) then throttle it back to match the 800gph of the eshopps.
What diamter pvc do i go with from overflow to sump ? The eshopps bulk head is 1 inch so im guessing 1 inch lol
From the pump to the tank would be 1 inch as well ?
Thiugh that the description for the dc6000 said it comes with 1 inch barbed fitting.
Also why are pvc preferred over tubing. Looks like i could get the tubing to match the eshopps ?
Would this be appropriate for the return to the tank ?
http://www.amazon.com/U-Tube-Directional-Return-inch/dp/B007Y7PATI/ref=pd_sim_199_3?ie=UTF8&dpID=21BeRd+HhLL&dpSrc=sims&preST=_AC_UL160_SR160,160_&refRID=19Z1FW4CVVC9CAQAT6A0
The overflow you posted will work fine, just make sure to clamp your hose on. The reason PVC hard line is preferred is because it doesn't have leak problems when it's done right. Many use flexible piping without issue, you just need to check for leaks a bit more often.
If you attach a hose to the U-tube the water will be pushing under the seam due to the direction of flow, so having a glued PVC pipe is a bit safer. The other option I'd suggest looking at would be the Fluval setup. The hose has no breaks between the sump and the top of the tank, so no leaks either. Here's are the links -
http://www.amazon.com/dp/B000256908...UTF8&colid=ZNZWDHHTFBG0&coliid=I2YX4BGJ8AQ275
http://www.amazon.com/Fluval-Bracke...F8&qid=1454218205&sr=8-36&keywords=fluval+406
http://www.amazon.com/dp/B0002Z7UFG...UTF8&colid=ZNZWDHHTFBG0&coliid=I15KD2JX9FRXB5
They all fit together for the flow back into the tank, you just need to fit the right fittings to attach it to your pump.
To address the flow rate. The 6000Lph/1585gph rate is also given at zero head. If the rim of your tank is 1.25 meters/4.1 feet above the pump, you're head needs to be calculated in there too. You'll also need to figure horizontal flow rate if you have a horizontal run.
So to look at this, if you're running the pump at 100% with a 1.5M/4.1 foot head, you're getting about 4000Lph/1056gph. But.. running the pump at 100% maxes you out, and isn't the best for the pump. Sooo... Run the pump on level 3 (old style pump) and you're now at 80%, or 844 gph - which is right in line with your Eshopps flow rate.