Hi guys.
As some general guidance, here are some things to look for in a system for this hobby:
Standard-sized prefilters, membrane, and DI cartridge
Brand name, high-rejection membrane
Specifications provided for each stage
Pressure gauge after the prefilters and before the membrane
Thermometer
TDS meter
DI bypass
Vertical DI stage
Refillable DI cartridge
Aluminum bracket
Quick connect fittings
No water from pressurized storage container delivered to DI
Flush valve
Clear housings
High-quality instructions
Customer support before, during, and after your purchase
A vendor involved in your hobby
If you have any questions - I'm happy to work through them here with you, or at the frag swap.
Russ @ BFS