Your benchmark results, given the sequential read speed, looks like SATA I speeds, which would be a bit under the theoretical 150MB/s of SATA I. The question is why that SSD is apparently operating at SATA I speeds. A 7.1 WEI with that benchmark? I don't doubt you, just interesting.
Did you try clearing the BIOS/CMOS on your board? That can be important with any new drive. Be sure you know what your BIOS settings are BEFORE you clear it, if you use anything besides the defaults. You really should check you are in AHCI mode after the BIOS clear just in case. Any SATA or chipset settings in the BIOS that may be significant? There have been many BIOS updates for your board, what version are you using now?
Do you have a benchmark of your 320 on that board?
Your AMD board has the SB850 SATA III chipset. I see you are using the msahci driver, which may not provide the best performance with your chipset. You could try the AMD AHCI directly from AMD. I have read that some AMD boards don't perform at their best unless the AMD RAID driver is used.
You said your 520 was removed from an ASUS notebook, which worries me somewhat. Was the 520 the OEM drive in that notebook? What is the model of that ASUS notebook?
This may lead nowhere, but start the SSD Toolbox, select the 520, and then click on Drive Details. Scroll down to Work 76, and check bits 3, 2, and 1, they should all be set to 1.
The freeze lock power cycling thing should not have bothered the SSD. The SMART data won't tell us anything applicable to this situation IMO.
Thanks for all the helpful suggestions. Just want to let everyone know there is nothing wrong with the Intel 520 SSD, the problem was due to my mobo's BIOS setting, rather unstable motherboard, the speed problem has nothing to do with the SSD drive.
The RAID setting on this mobo has to be set to IDE otherwise you won't get any good speed out of the SSD. I remember it was set up correctly when I first built the computer 2 years ago, but after re-starting the computer a few times last night, I realize the motherboard can have trouble remembering the BIOS setting after each re-start. I didn't to bother check this part when the compuer still had the Intel 320, no benchmark was done either as it wasn't build for speed, rather reliability.
Everything is working now and the 520 scores 7.9 under WEI. As far as the speed goes, it is good enough for my work load and I am going to just leave it like this for the time being. Will try the AMD RAID driver if I have the chance.
Here is a snap shot for the 520 SSD's benchmark.