Memory is upgradeable to 2x16 = 3G;  DDR4-3200 or -2666 supported.

SSD can be upgraded as well;  depends on whether you want a 2.5" drive to replace the hard drive, or to install or replace an M.2 SSD (NVMe). Both options are available.

I have found that there's a Slot for and SSD NVMe PCIE3 x4...  I don't remember this on the specs. Can I use it?

The free slot is just next to the actual NVMe and you can read on it: "SSD#1 M.2 2280 NVMe PCIE3X4 SATA"

Any RAM os SSD NVMe that you recomend? Should i go for 2666 ram or 3200?

Hi @ricko3d   Alienware m17 Setup and Specifications Table 1. Storage specifications says Interface type PCIe Gen3x4 NVMe, up to 32 Gbps, Capacity Up to 1 TB.  

Alienware m17 Gaming Laptop 

Hi @ricko3d  is there some reason why having three storage drives is not being considered? Take the rear panel off and have a look at what storage drives options your m17 has. Guess you could keep the 1TB (+8GB SSHD) Hybrid Drive and just add another M.2 2280 NVMe, to have two NVMe drives. 

Hi @ricko3d  Alienware m17 Setup and Specifications, Table 1. Memory specifications says system board supports RAM Speed of 2666 MHz. The system will default to the system board capabilities, so getting a higher speed RAM card will not give a memory speed increase.  

My personal Configuration would be keeping the HDD with the 8Gb of cache and then I'll add a 512gb SSD for the boot drive for personal files I need to access fast and store games and apps on the Other drive.

Here's a basic thing on how to insert M.2 Sticks into each slot.

SATA M.2 can ---> into NVMe M.2 slot

NVMe M.2 can't --/--> into SATA M.2 Slot

Hi @ricko3d  if you decide to have two NVMe drives, you may also want to swap out the Single and install the Dual Hard Drive Heatsink R46DX 0R46DX. 

Thats useful for conducting heat.

Hi @ricko3d   Dell has provided M.2 drive guidance in knowledge base article SLN301626. 

Have you consulted the Dell m17 Documentation and Manuals to determine what your system board will accept? Have given you the specific links in my previous posts. 

I will go for 2x16gb ram at 2666, that's ok.

Im getting confused at the SSD, my setup already is: 1TB HDD + 8 MB cache, plus a 512 GB NVMe SDD, and I have one FREE SLOT remaining for another SSD, which now I now. 

Thing is, you can read on there "SSD#1 M.2 2280 NVMe PCIE3X4 SATA" then ,as you say:

..."Here's a basic thing on how to insert M.2 Sticks into each slot.

SATA M.2 can ---> into NVMe M.2 slot

NVMe M.2 can't --/--> into SATA M.2 Slot"...

I don't now where to start looking at, whats the difference? I'm trying to find out when buying but is not that clear.

can't find it anywhere, is there another option for replacement?

What I was saying is that you can insert a Slower SATA 3 M.2 SSD inside of a NVMe slot but you cant put a NVMe drive into a SATA M.2 slot because of a physical incompatibility.

That's what I meant.

@ricko3d  - I'm in the same boat, I want to add a second NVMe or a 2.5" SSD to my m17 R1. I still can not find the proper 2.5" mounting bracket for the SSD slot. Keep in mind, if you have the 90mAh batter you can not install an SSD. You have to have the 60mAh battery.

Here is the part you need to install a second NVMe drive:

https://www.amazon.com/dp/B085WM6RDD/?coliid=I2HS10KA3CBMRS&colid=20OBZF2N3A1KD&psc=1&ref_=lv_ov_lig_dp_it

It would replace the single-slot heatsink you currently have.