I don't have (maybe one or two) 32 bit plugins, and before I paid much attention, my search path is getting long, and I have more than a few dupes in the path as well. So... I would like to make a VST2 and a VST3....well, actually I would really like to dump them all in one folder on my D drive. I have everything I need to make good music, so won't be gas'sing for plugins. Nectar and Ozone will get me thru the parts I am still trying to grasp. 
 
Is there any down side. other than paying attention when VSTs get installed, to having them all in one place? They would all like to be in their own company folder, but easily bypassed.

I too have/had difficulty in keeping track of where everything was installed having so many paths in VST scan I knew I had duplicate scan paths and things were being scanned sometimes twice.  A fellow Forum member came to my rescue.
 
Bitflipper developed an Excel spreadsheet that details your plugins/type/version#'s/locations etc. 
Search the forum: plugin inventory.  Look for "plugin inventory" thread by Southpaw3473 (Nov 29, 2014)
Go to post #67 and there will be a dropbox link from Bitflipper.
 
It may still be at this location.
 https://www.dropbox.com/s/ulmt0wg458485lx/VSTInventory107.zip?dl=0
 
A wonderful housekeeping batch job, outputs to an easy to read XLS file -made it quite  easy to clean things up.
 
Bill -

Bear in mind you cannot simply move all of the dll's from one folder to another.
 
Many of them need to be re-pointed by reinstalling or in some cases, the registry keys modified.

Not a problem, I don't have all that many to reinstall..

Be careful with VST3 plugins. To date Sonar is the only program that has provided a choice for installation location, though by default it is the same path I've listed below.

Every other developer I have plugins from uses the default Program Files/common Files/VST3 folder without an option to change it.

All the advice on this forum has always been to keep Programs and Plugins on the same drive. It's not like sample data that gets read in and out of memory as the samples change. There's no advantage other than organisational. But which drive will you put them on? With samples? With Projects, by themselves?

I have close on a thousand plugins but they don't take up that much space comparatively. It's only sample libraries and projects that take significant amounts of space.

You probably don't have many DX plugins but they can't be moved around at will. Certain files during the installation process are entered in the registry. VST plugins are scanned by the host and registry entries created that way.
By default developers actually look for a system VST plugin folder which by many is considered as C:/Program Files/Steinberg/VSTPlugins. I use the path "C:/Program Files/VSTPlugins/ folders by developer" if you have plugins from a lot of different developers. By doing so, Sonar creates folders in the default plugin layout instead of one long continuous list which can easily get wieldy once you have a list comprising 39 or 40 plugins or more as in my case.
One other point. Not all developers give you a choice of where to put VST plugins of any sort and will insist on their own location. However I've found that when moved manually when updates are installed, most respect the new path.
When you encounter manufacturer folders within the C:/ Program Files tree these are usually for support files and often for .exe files if the plugin has a standalone version. The plugin dll is never located with those files so don't get it into your head to just move those folders thinking it's OK. It ain't. Except of course when the support files are manuals. There's lots more to learn but that should get you started. Maybe you know all that anyway, in which case don't be offended by me treating you like a complete newbie.

I only have a few 3rd party.. Line 6 Izotope Positive Grid S-Gear Toontrack. Oh, and the free Blue Cat Bundle. That's pretty much it. Everything else came with Sonar. I have ALL of the installs as well so no biggie, and no presets to lose... I'll use that path and get them together. I am way more concerned with getting the tunes cut than collecting VSTs at this point. I just need em to work and be understandable by me!

In addition to the good advice above, I suggest:
 
VST3:
Leave them to go under the 'standard' location.
 
Cakewalk (VST2):
Leave them under %CakeHome%([\vstplugins],[\x64\vstplugins]), as per default installation, for simplicity.
 
VST2 / 3rd Party:
Maintain 2 'top' directories - 64bit and 32bit (if using) ... because sometimes each variant has the same DLL name.
 
See my guide:
(written wrt Steam MC6T / Sonar X3 - but generic / transposable)
Shell's Probable Guide to VSTs - Location, Strategy and More

Just read your treatise good stuff.