Dedicated DAW Build - 2 drives or 3?

Hi, I'm retiring my overworked laptop for a ground-up dedicated DAW build.  My question is should I use 2 drives or 3 if I am using SSDs.  
 
Using 2 drives:
C (SSD 500 GB): OS, Cakewalk Program, VST folder, Content folder, Command Center
D (HDD 1TB): Projects
 
If I were to use 3 it would look like:
C (SSD 240 GB): OS and Cakewalk Program
D (SSD 240 GB): VST folder, Content folder, Command Center
E (HDD 1TB): Projects
 
My thinking is that during recording, the application, VSTs and Projects are most active.  I know that the seek speed of SSDs are much faster than HDDs suggesting that 1 drive for everything except Projects might be enough.  Are there other significant factors like throughput (too much info in the pipe)  Would a 2nd SSD allow better throughput into the board?  (Please forgive my lack of accurate language.)
 
Thanks
 

silver son
 
If I were to use 3 it would look like:
C (SSD 240 GB): OS and Cakewalk Program
D (SSD 240 GB): VST folder, Content folder, Command Center
E (HDD 1TB): Projects
 Would a 2nd SSD allow better throughput into the board?  (Please forgive my lack of accurate language.)

Not for this config. I have all of X2, X3 and Platinum (multiple versions), all the Rapture free and paid expansion packs, a few DPro packs and hundreds of plug-ins installed on my system 240GB SSD with plenty of room to spare. From a performance perspective, there is no reason to break out VST binaries and Cakewalk Content to another disk. I did put the Command Center cache on my project drive using a directory junction though to have a large area for quick access to old installers.
 
As Jim mentions if you use other sample-based software, in my case Superior Drums and  BFD, those samples are on a third drive. I do not use Kontakt or any of the other major sample-based synths but they would have their libraries on drives other than the system or project drives too.

 I have 4 total.  I still don't get why people think it's convenient to put VSTs on a separate drive.  Most of them are small unless they are romplers.

bitflipper
I plan on adding a 4th drive, a 1TB SSD, for sample libraries when I can afford it. 1TB SSDs are still kinda pricey, but will no doubt keep coming down.
 
I remember the first time I saw a 1 GB disk drive. It was the size of a dishwasher and cost $50,000. Incredibly, they actually trusted me to take them apart and put them back together again. Some years later I bought my own 1 GB drive for $180. Now I've got the equivalent of 2,500 of those in my current computer. 
 
Anybody keeping track of 1TB SSD prices?

All of the time.  Way too much for me. Meanwhile I also keep track of HHDs.  I've seen 1GB WD Blacks under $80. I see some WB Blues 2TB for under $80. I may have to upgrade a 1TB to 2TB. My drives could be featured on an episode of Hoarders.
 
 If I had a board with 12 SATA ports I'd be buying those 500GB SSDs.

I have the following setup:

1. SSD 120GB: OS, Apps, VSTs
2. SSD 120GB: Multisamples + libraries (e.g. drum maps, templates)
3. SSD 120GB: Current & recent projects

Plus other non-SSD drives (some partitioned) for storing the following:

• Older projects
• Exports & mixes
• Misc music-related stuff
• Manuals & reference material
• Software installation files
• CCC downloads
• Visual media
• Backups

Obviously some users need a much bigger drive for multisamples than I do.