I am configuring to order a new Alienware Aurora R-7 desktop.  Looking at: i7 8700K; NVidia GTX 1080 Ti w/ 11 gb DDR5X;  32 GB DDR4XMP at 2933 Mhz (dual channel hyper X); and 850 Watt power supply w/ liquid cooling.

I play large simulation games, (Cities:Skyline/Trainz etc) with lots of mods and themes downloaded from Steam, so besides what I need to run the game, and also to create content... I need lots of storage for those saved games;  I make large, long, high def video genealogy movies for clients- so need both speed and memory for video/sound editing;   I also create in photoshop and do exacting photo editing. Everything has to be eventually burned onto DVD and not have it take 5 hours.

Normal online genealogy research work, documents, email, you tube viewing and personal photos are currently all accessed and used on my old Gateway with Windows 8.1 (not updated for 4 years now), i5 3330 processor desktop- which has a 1TB hard drive, 8gb DDR3 memory and just a Nvidia GTX 650. I will continue to use it for all that until it dies (which it will always do- and yes...this data I back up frequently).

(Finally)- here's my question(s)...

I was looking originally looking at combining a 2TB M.2 PCle NVMe SSD (listed as boot) with a 2 TB 7200 rpm SATA HDD (listed as storage). 

Since SSD drives seem to be touted as so much quieter, and so much more reliable and faster than a hard drive... do I need to have BOTH (given how I am going to use the computer)?? 

And if  I CAN use just one or more SSD drives and if I can even GET that configuration from Alienware,  (yes I know they are much more $$), then what's the size(s) I should aim for... will 2TB's be enough for all I do?

Anyone know what the largest combined size(s) of SSD(s) can actually go in my configured Aurora R7? Or any problems with only having  SSD in it?

Thanks for any answer!