Macbook Pro (mid-2012) is running very slow, even after upgrading RAM and SSD

First of all, thank you to the helpful people who responded to my original question.

Basically, my Macbook freezes periodically and gives me the spinning beach ball every thirty seconds or so (sometimes more often than that). After 45-60 seconds, it'll start working again, but then it'll freeze again 30 seconds later.

I took the advice in the thread I linked. I upgraded to 16 GB RAM and a 480 GB SSD, but it seems that hasn't fixed the problem.

EtreCheck version: 3.0.5 (309)

Report generated 2016-09-28 20:15:59

Download EtreCheck from https://etrecheck.com

Runtime 25:46

Performance: Poor

Click the [Support] links for help with non-Apple products.

Click the [Details] links for more information about that line.

Problem: Computer is too slow

Hardware Information:ⓘ

MacBook Pro (13-inch, Mid 2012)

[Technical Specifications] - [User Guide] - [Warranty & Service]

MacBook Pro - model: MacBookPro9,2

1 2.5 GHz Intel Core i5 CPU: 2-core

16 GB RAM Upgradeable - [Instructions]

BANK 0/DIMM0

8 GB DDR3 1600 MHz ok

BANK 1/DIMM0

8 GB DDR3 1600 MHz ok

Bluetooth: Good - Handoff/Airdrop2 supported

Wireless: en1: 802.11 a/b/g/n

Battery: Health = Normal - Cycle count = 1099

System Software:ⓘ

macOS Sierra 10.12 (16A323) - Time since boot: about one day

Disk Information:ⓘ

OWC Mercury EXTREME Pro 6G SSD disk0 : (480.1 GB) (Solid State - TRIM: No)

EFI (disk0s1) <not mounted> : 210 MB

SSD Replacement 09-25-16 (disk0s2) / : 479.76 GB (397.09 GB free)

HL-DT-ST DVDRW GS31N ()

USB Information:ⓘ

Apple Inc. Apple Internal Keyboard / Trackpad

Apple Computer, Inc. IR Receiver

Apple Inc. BRCM20702 Hub

Apple Inc. Bluetooth USB Host Controller

Apple Inc. FaceTime HD Camera (Built-in)

Configuration files:ⓘ

/etc/sudoers, File size 2299 but expected 1563

Gatekeeper:ⓘ

Mac App Store and identified developers

Kernel Extensions:ⓘ

/Library/Extensions

[loaded] com.Apowersoft.driver.AudioDevice (1.6.7 - SDK 10.11 - 2016-09-25) [Support]

System Launch Agents:ⓘ

[not loaded] 7 Apple tasks

[loaded] 169 Apple tasks

[running] 95 Apple tasks

System Launch Daemons:ⓘ

[not loaded] com.apple.jetsamproperties.Mac.plist (2016-08-25) [Support]

[not loaded] 40 Apple tasks

[loaded] 161 Apple tasks

[running] 102 Apple tasks

User Launch Agents:ⓘ

[loaded] com.google.keystone.agent.plist (2016-07-11) [Support]

User Login Items:ⓘ

Dropbox Application (/Applications/Dropbox.app)

Google Chrome Application (/Applications/Google Chrome.app)

Internet Plug-ins:ⓘ

QuickTime Plugin: 7.7.3 (2016-09-13)

3rd Party Preference Panes:ⓘ

None

Time Machine:ⓘ

Auto backup: YES

Volumes being backed up:

Destinations:

SSD Replacement 09-25-16 [Local]

Total size: 0 B

Total number of backups: 0

Oldest backup: -

Last backup: -

Size of backup disk: Excellent

Backup size 0 B > (Disk size 0 B X 3)

Top Processes by CPU:ⓘ

6% WindowServer

6% netbiosd

5% AddressBookSourceSync

5% Google Chrome Helper(10)

3% kernel_task

Top Processes by Memory:ⓘ

1.09 GB kernel_task

590 MB Google Chrome Helper(10)

262 MB mdworker(8)

131 MB Google Chrome

98 MB Dropbox

Virtual Memory Information:ⓘ

12.00 GB Free RAM

4.06 GB Used RAM (987 MB Cached)

329 MB Swap Used

Diagnostics Information:ⓘ

Sep 27, 2016, 10:17:15 PM Self test - passed

Sep 27, 2016, 05:17:12 PM /Library/Logs/DiagnosticReports/nsurlstoraged_2016-09-27-171712_[redacted].cpu_ resource.diag [Details]

/usr/libexec/nsurlstoraged