My rig is already 3 years old and currently sits on this specs:
 
EVGA 790i SLI Ultra 132-CK-NF79 (BIOS P09)
Q9450 @ 2.6Ghz + Thermalright Ultima-90
Corsair XMS3 DHX 2048MB DDR3 SDRAM PC3 12800 @ 800MHz: CL8-8-8-20 (TW3X2G1600C9DHXNV)
EVGA 9800GTX+ 512MB
 
Im looking to upgrade for a new pair of memories since today im really limited on new games with those 2GB, i was looking foward to bump it to 8GB of memory and also upgrade the graphics card to something that would be more up-to-date but not bottlenecking my Q9450 wich i can OC to 3.6Ghz without problems (used to run it at 3Ghz 24/7)
 
I have seen that most modern memories are 1.5v (low voltage) wich im not sure if they are compatible with the 790i chipset, and the old 1.8-1.9v are discontinued, wich memories would you recommend me that can be run smoothly in 8GB (4x2GB or 2x4GB) and fully compatible with the mobo?
PD: I would like a low latency memory, since i like to overclock with my sytem :P
 
Also im looking for a EVGA 560GTX Ti as a replacement for the 9800GTX+, your opinions?
 
Thanks in advance.

Go with Patroit Viper Series PVS34G1600LLK Memory If you can find them I know some Fry's carries them. I running 2 EVGA GeForce GTX 560 Ti Maximum Graphics Edition Crysis2 with no problem. See my sig for my specs.
Jim

I've been running a 790i for 3 years too. I had 8g of older Reapers which were working great with my Q9550 OC'd to 3.8.
 
Last changes I made on my 64-bit OS was for 8G of  Patriot PGS34G1600ELK @ 1.8v. That was a 8G recommendation by a tech at EVGA. Later I installed a QX9770 and ran it at 4.2 with OCZ Blade E ST - p/n OCZ3BST2000LV4GK @ 1.65v. It run flawlessly.
The 790i is can be finicky about 8G kits. I've  monitored RAM usage and it comes close to 4G in-game. I like head room so this is why I run 8G. I think it runs better. But, I have run on 4G with great results too.
 
For gaming, Bandwidth how I measure chiefly. I play BFBC2 a lot with two 580's, and just one card can handle everything. Also I bought my son two 570's and he's getting 60+ FPS on a maxed out 3D setup. That won't happen with the Ti's.
 
I also have a single GTX480 on a 780i SLI/Vista -64 Ultri/8g of Patriot 1066.  NO OC and it gives 60-75 FPS with everything maxed.
 
So, if you can afford it, GTX 470 or 570 will get you all the performance and eye candy their is today and more.

Looks like those Patriot PGS34G1600ELK are still on the market, thanks for your advice!
By the way @ZelmoQuad could you post your BIOS settings for running those 4x2GB, i guess that you had to loose the timmings and bump the SSP/Mem volts right?

Anyone else have another memory recomendation?