When I say the best of both worlds.....Really depends on your DIY capabilities, but can easily be done with an already built tank or building from scratch with acrylic.....A lot of times when you "store buy" your limited to what you get. If you build from scratch or another method, you can custom tailor it to your exact needs and wants. Prebuilt sumps are just like cars.....You get what's on the "show room floor".....If you want add ons and all that it costs you additional. By building your own, you get what you want right out the door.....
I'll use the acrylic method as a good example. You can measure what your available space is under your tank......Before you purchase or build anything the first piece of equipment I would try to decide on would be what skimmer I'm going to use. With the skimmer choice/purchase out of the way; you build the sump around that skimmer choice. A lot of prebuilt or store bought sumps, might be impossible to fit your skimmer choice into.....And again with your better than average or custom built sumps your talking not only big money, but shipping becomes a major factor in cost.
After you've made your skimmer selection, it becomes a bit clearer what size sump you actually need....With that said you want the skimmer to easily fit in that compartment. Another option you might want to look at or be considering is do I want to be able to employ the use of filter socks.....Not critical, but at some point you might want to use them for whatever reason it may be.....Also you want your sump to be able to handle your flow through the sump.....To small a sump and to big of a return pump you'll have issues with micro bubbles being forced into the return area and in affect being forced back to the tank. This is problem seen quite a bit IMHO......Again some of that can be solved with properly sizing your return pump, but at times it's just not that simple. There are times you have to go to an oversize pump to overcome a head pressure instance, which might facilitate a bigger pump; which might of course flow to fast through your sump.....Another thing you might want to look at is the sump going to afford you the comfort of housing you other equipment. You'll see that through purchasing equipment heaters alone, can be rather bulky/long.....Quality heaters IMO aren't small and do present a challenge to fit into a sump......Again my pure opinion is a lot of pre made sumps are limiting in this facet as well.....
I'm not saying you can't get a quality, nice sized pre built sump from the LFS, but be prepared on cost as well......I think I'm rather spoiled in the fact I prefer to custom tailor and build everything possible to my exact needs and once. With this hobby as you already know nothing is cheap, so why skimp and buy exactly what you want the 1st time. Nothing worse than skimping and settling for 2nd best only to have to repurchase it again months down the road.....
As to the topic of RO/DI units......If your asking or inquiring about buying a drinking unit from a Lowes or HomeDepot......Nah.......I'm not saying it can't be done, but there are specific areas of the unit you want to look closely at. Again with the expense of the hobby, do it right the first time.....Again in this area, I built my own unit, but I'm comfortable doing so, but you can get a quality unit, from places like **************, AirWaterIce, SpectraPure......To be honest, SpectraPure probably has some of the nicest units out there, but again cost might be a factor when looking at that brand as well. With the units I mentioned briefly you can get the valve and holding tank to make drinking water for home/personal consumption if you'd like......
