I have had quite a bit of experience with laptops that run off of SSDs. This experience, contrasted with my desktop gaming PC's lack of any SSDs, leaves me a bit disappointed when it comes to booting up the PC, or starting games, or overall system responsiveness.

My Desktop PC is:
Intel 4690K
MSI Z97 Gaming 3 Motherboard
16GB Ram
GTX 970
1TB HD (Windows)
250GB HD (Linux).

There are a few options available.... but I'm not sure which would be the best bang for my buck.

1. Install a M.2 SSD to act as a boot drive, that will hold the OS and a couple of frequently played games... utilizing the 1TB drive for bulk storage, and the rest of my Steam Library
2. Install a Firecuda Hybrid Drive (SSHD), and simply use the included transfer solution. 
3. Upgrade my Motherboard, Processor, RAM, and get OPTANE. 

The third option isn't really that much of an option since I think it is by far the most expensive of all 3 propositions. Optane seems like a great option, provided you already have the motherboard and CPU that it requires to be able to run.... like a cheaper option compared to 1 and 2. Perhaps a year or two down the road, I might go back to this option after I full system upgrade.... but right now, I just can't justify spending upwards of $400 upgrading my CPU and Mobo. 

So that really only leaves me, realistically, with options 1 or 2. 

Option 1, would be marginally faster.... but provide me with only marginally more storage. 
Option 2, would be slower, but allow me to purchase a larger drive. For instance, I can get a 2TB SSHD for only $90 or so on Amazon.com.

That being said, I have no idea how well SSHD compares to an M.2. Most online comparisons are between SSHDs and Sata SSDs. So I am just going to have to ask if anyone here has any experience with both options, and knows whether or not SS Hybrid Drives really are still a good option? 

You want an M.2 SSD. It's head and shoulders above a SATA3 SSD.

Google the specs of a Samsung 850 pro (SATA) and a 960 pro (M.2). No contest. 

ETA: I have a 500 GB 960 Evo for the windows boot drive. I also have a 4TB spinning hard drive for storage. All my Steam files live on the 4TB except for Doom 2016. It lives on the M.2. Well worth it for loading times.

The problem that I've heard of having this set up, is constantly having to manually choose which drive to install various files, programs, etc to.

Also, if I were to add an M.2... it would be quite complicated to migrate Windows over to the M.2 SSD. As far as I understand, it would make more sense to just backup all my important data... and then format my 1TB, and start off with a clean new install if Windows 10. This isn't exactly something I'd really look forward to. Unless of course, there is some sort of better solution out ther.e

Assuming Sata 3, the extra cost for an M.2 just isn't worth the miniscule ACTUAL performance difference.
NTFS just will not allow you to take advantage of the throughput.
Your biggest improvement comes from going to spinner to SSD period, and that is because of the negligible seek times on the SSD.

Nick

Those are all reasonable points, but this is kind of a pay to play issue. A 500 TB 960 EVO is "only" $234 on Amazon.

If you're going to do a clean install of Win10, do yourself a favor and get an SSD. You will never, ever go back. Realize that you'll be copying your steam folder back and forth to your storage drive. I would never "migrate" windows. If you're changing boot drives, always do a clean install. Then make a disc image of it and you'll be golden when it comes time for the next reinstall.

Or, just pony up and get a 1TB Samsung 960 EVO. $460. Buy once, cry once. 

I guess a solution I didn't think of...

Purchase an M.2 SSD, and a 2TB HD. Do a clean Win10 Install on the m.2, with the 2TB drive designated as my mass storage/game library device. Keep the 1TB HD and migrate over any documents, important files, photos, etc. Then, I can just "retire" the 1TB HD as an archived HD and just let it figuratively collect dust on a shelf somewhere... just in case I later realize I forgot one other thing or two that I needed to migrate. That way, I don't have to worry about permanently losing something. 

I'll have doubled my storage capacity, increased the speed substantially, AND have the peace of mind knowing that my prior Windows install is still backed up somewhere in case I forget something.

My rig has four drives, two SSD and two HD.

SSD #1 is Windows boot and productivity apps.
HD #1 is user folders and games.
SSD #2 is Intel SRT cache and accelerates HD #1.
HD #2 is random junk storage.

This will accelerate the OS, all apps, and your most frequently played games and accessed user files. Intel SRT supports max size of 64gb which will be cheap and much larger than any SSHD cache.

Sounds like a great idea!

My motherboard, apparently, doesn't support NVME, however.... so it doesn't really make sense to get a M.2 NVME SSD... and instead go for a 2.5" SSD. However, 2.5" SSDs don't seem to come in 64GB..... should I instead use a 64GB m.2 SSD ?

So you know, you can get a PCI-NVMe adapter card. Install the NVMe SSD on the card, insert the card into a PCI-express x4 slot. Now you can get your full NVMe speed and not be limited by the SATA bus. If using it as a boot drive (which I'd recommend), you might need to tweak some BIOS settings to boot from a PCI source. 

Here are some examples:

https://www.newegg.com/Product/ProductList.aspx?Submit=ENE&DEPA=0&Order=BESTMATCH&Description=nvme+pci+card&N=-1&isNodeId=1

Intel SRT is older tech when SSD wasn't scaling out to larger capacities yet. You can however use a greater capacity SSD with SRT but it caps at 64. The unused portion you can supposedly partition to use as another drive but I haven't tried that. I think I used a 80gb and just left the rest unused. If you can find a cheap SSD to use as a cache drive to accelerate a big HD for your steam games, it's probably an affordable solution until newer tech becomes more cost effective like optane.

ETA: SRT also saved my ass when the SSD cache died. Since the data was stored on the HD I just disabled caching, swapped in a new SSD, re-enabled caching and let it figure out the cache pattern again. Most SSD controllers shouldn't toast as easily but again this was with the early SSD tech.