Ditch the Sempron 145. Get's clogged with Windows, drivers, interrupts, sgminer at high intensity, VNC or teamviewer, cgwatcher, MSI Afterburner and so on. Get a dual-core Sempron 190 for $5 more.
i've built eight sempron 145 in 4 card configs with no issues whatsoever. nothing gets 'clogged' with a single core.
I've also successfully installed on core solo, Athlon x64, and triple core athlons, so slower CPU works fine too.
PSU : Nilox Line Interactive 2100VA Server 17NXGCLI20002
CABLES:
total 6 riser usb 3.0 .. 1 meter lenght
the USB3-connector risers look awesome, and give lots of config flexibility. i want to try some out, but they are 3-4x as much as the equivalent ribbon cable risers.
super smart to use a UPS with line conditioning. most people don't think that far along.