RPi 3, great build quality, but excessive heat under load (hits 85’c very quick), heatsink recommended, or, heatsink/case combo: https://cogent.design/
Personally, i would go with the Odroid C2. Gigabit network with throughput to match (990Mbit~), great CPU and solid 24/7 system: http://www.hardkernel.com/main/products/prdt_info.php
Although, out of stock at the moment.
Another option for a good server, NanoPi M2. Good CPU and gigabyte Ethernet performance, however, does need the heatsink:
From personal experience. The best performance, stable SD card for price is:
Sandisk Extreme (40-50MB/s write)
Sandisk Ultra are great for budget, but lack write speed (12-17MB/s).
I use Sandisk Extreme for all testing in DietPi. The increased r/w speeds make a massive difference to file-system IO and general performance “snappiness”.
Try and avoid Transcend, and, non-branded SD cards. In my experience, guaranteed file-system corruptions.
If you get any Odroid, make sure you snap up a EMMC module, the 128GB module does 150MB/s r/w on C2. Makes SD cards feel like a snail. In terms of performance, its like changing from a spindle HDD to SSD in a PC.
Performance of EMMC is awesome I have 64GB in my XU4
received 2x 64GB EMMC for the Odroid C2’s (still waiting for the boards). out of stock reseller is waiting for shipping from hardkernel