Now we're talking!
The size of your refugium & contents should be dictated by the space you have to work with. Bigger is better, but anything is better than nothing. If that means a little 5 gal like mine so be it, if you want to go nuts, make a room in your basement, make it your filtration room & plumb it to the livingroom upstairs, rubbermaid makes great 100gal feed sumps...
Decide what you want the fuge to do; nutrient export? breeding ground? denitrification? is it the sole form of filtration for your system or just supplimental? calurpa is the standard "green", but you have many choices out there, mangroves are great but large #'s are needed, I've heard 1-2 per 5gal is a good rule of thumb, but again is this your sole means of nutrient export? If you have a ridiculously huge bioload you will need a ridiculously huge filtration system. Thats why there are no hard and fast rules that work for every tank as every tank is different.
UV is a great add on provided you don't undersize, & you realize it will also kill benifitial organisms as well. One solution is to only run the UV a couple of times per month.
Ca Reactors are great, costly initially, but the method of choice for Ca & Alk. If you are going LPS, SPS & Clams it is a must, but if your only doing softies you certainly won't need one.
Why would you want a fluval? what are you using it for?
Set up should be organized, efficent, not redundant & cluttered. It will just make maintenace chore a big hassle. If something goes wrong, servicing equipment has to be easy to do, did you remember those union valves? You'll find out the day your pump fries & you need to get it serviced!