I have a fair bit of extra cash and I think I'm finally going buy a Qnix 2710 1440p monitor (one's on Craigslist in my area for $215 and if it checks out when I try it I'll buy it), and that makes it time for some more GPU horsepower. I already have a Titan, so it would e less hassle to SLI but it wouldn't really cost any extra to go either route. I can get a pretty good 1150+MHz OC stable on my Titan now, but undoubtedly 1300+ on the Classified will yield a fair bit better performance. That brings us to the age old VRAM question again :P. Any thoughts from you guys? I know many will say to keep the Titan, but I'd like to see if there are some good arguments for the 780Ti side.

Thanks for the response! I've actually considered Dell's 24" 4K panel, but that would render me unable to get another GPU right away so I'd be pretty stuck on the gaming front. I will most likely upgrade to the next gen of nVidia GPUs (880) when they come out, so that would most likely be a better time to investigate 4K. But would it be better to just get the 4K panel now and wait on the GPUs?
There's also games like CoD Ghosts where even at 1080p it uses boat loads of VRAM, so there's an argument for the TITANs side.

Titan SLI.

If you know that you want that 4K Dell monitor, and you also know you will be interested in the 800 series from Nvidia, it may make more sense to skip the 780ti's this round and wait. I guess a lot of it depends on how much money you are willing to commit to this crazy hobby of ours. 
 
4K is just so demanding right now. I consider 60FPS as a playable frame rate. (and I don't like to bottom out too far below that) And it just takes so much to drive that type of frame rate at 4K. I am personally waiting on new 21:9 ultra wide monitors from LG and Dell. Its like the Dell U2913W, only instead of 2560X1080, its 3440X1440. I love the 21:9 aspect ratio, and the fact now that you can have that 1440P vertical resolution. Now I figure that still pretty demanding for SLI 780ti's, but not as bad as 4K.
 
I would start looking at benches for single Titan cards at 4K. If you perhaps thing 30 FPS is good enough with the games you like, you may do just fine with one Titan. Get the Dell 4K monitor, and then down the line, invest in SLI 880's. (whenever those come out, hopefully no later than this summer.) I think you will be in good shape either way.

For me, the big attraction for 4K is the screen real estate in productivity software. Games are not optimized for it as of now, and I agree it will most likely take a little bit of time before it takes the place of 1440p as the "enthusiast standard". However, if AMD keeps the pressure on nVidia and stays competitive, we may see 4K handling GPUs sooner rather than later. Four Titans are almost necessary to provide smooth gameplay on good settings with a 4K panel, and even then you're not getting much more than 60FPS.

Triss
Get another titan, with settings turned to max at 1440p in AC$ i've already passed 2900mb of vram with my gtx 780 :( , If i was to buy another card i'd want 4gb of ram as a min

Well, if it's available, what's wrong with the game using it? (so long as it's not crashing)
Look at like this, what if you had the Titan and 6GB of VRam, and the game was using 5.9GB, would you then be looking for card with even more VRam?