For a low budget rig, first play takes basic rig components. If you can buy them cheap, you overall income will be better in time, since every card need to pay for basic components first.
In my situation and by logic, if You can, 1080ti will be best option space-wise. (With 6 gpu MOBO you got better exploatation cost per PCI-E).
1080 ti will hold value better because of being top tier right now.
It really depends on what "low budget" mean for You
For alternatives... 1070 were way to go, but if You thinking into reselling them later... You'll have hard time when all 1070 hit second hand market

As far as i see till 40000 block it's still hybrid. By 'running staking node' i mean I'm mining on my rig and hosting staking wallet with my mining earnings on my personal PC for 24/day
I've got good feelings too, POW/POS hybrids with mining phase are by far better option than ICO in my opinion since it's more fair. The only thing that takes my concern is how much total supply will be when 40k block will be discovered since POS blocks count towards it.

Yup, but for now for 800-1000$ you can get brand new 1080ti with 2-5 year warranty (Zotac AMP Extreme Core are at 1200$ with 5 year now).
So when counting resale value take into account manufacturer warranty as 1-2 years warranty with 1080ti investment after ROI vs no warranty at all with 1070, you will end up with 1080ti resale value being better than 1070.
Edit:
Also don't take current ROI into consideration.  To be fair and honest vs yourself always try to put your ROI at reasonable point of 12m (Gaming cards are suitable for around 8h of full load daily, as it's commonly used as "extreme" calculation, so with 3yrs warranty You are "wearing out" card to zero in 1 yr by using it 24h). Then if you can, don't cashout daily. Sell when it's high, never when it's dumping. You're hurting yourself with selling at dump. eg. I've mined ~18k dgb from start of this month. If I'd sell at dump i'll end up taking loss of about 20-40% contrary to hold all, and selling yesterday at ~2.3 cents per each. Some days they were touching 0.8 cent/ea.

With current violate movements on GPU market i can't really take into consideration 1080ti price. Even now in my country you can buy it depending on manufacturer from ~800$ to ~1400 with liquid cooling.
I've bought mine (because of reseller messed my order with violation of law) at around 650$ price counting USD today ratio. So yeah, effectively FOR ME it's best of all.
I've been running GPU rendering too, so that points my ROI to few projects and mining is nice, pretty "stable" addition to what I can make
Edit:
Eg. 3 weeks ago price for Gigabyte Gaming X was 1200$ from 900$, now it's 1100$ from about two days.*
*basing on current usd ratio

I've used one included in Nemos miner, https://bitcointalk.org/index.php?topic=1777336.0
As I stated above... Since not having full rig now, I'm kind off of _sp modded mineable coins He's doing amazing job but when the mod hit miners difficulty skyrockets, and it's really hard to make reasonable profit without _spmod but buying it is kind of gamble with 2 cards. If you have higher hashing cap just follow _spmod thread, he's always on wave

Well, even before a mining BOOM 1080ti was kin of hot product in my country, so since I'm going to upgrade my rig, 1080ti suits me the best.
From start (late may) 1070 have better ROI when i checked but even at the bubble peak it was about 2-3 days.
Counting resale value, rigs density, technological advancement... Yea, I won't even look at 1070 now. But they can be better for high density rig or for starting with low investement.
But to be honest even in high density rig it's really better to have 6 cards hashing like 15, than the other way.
 

Cant find much info on Myriadcoin, well there is pretty big thread here, but it looks like there is no movement at all. Difficulty is pretty high but on 1x1080ti it should be 1k+ coin per day on skein.
Sadly only pool that i could find with it is MiningPoolHub but miners on multicoin port hopping on it when diff decreases with like 50x 6xrigs screws my daily earnings with their share rate.
I've similiar issues with setting solo mining as with DGB skein tho.
If someone could help me with setting solomining MYR i'll drop a block reward or two... ^^

I've tried HUSH and ZEN, they both gave better results than from miner being comparable to DGB mining at that time but equihash ends up producing more heat.
They have some possible future but I don't really believe in fork of forks but removing some flaws from original put  that disbelief at wager.
Still looking for some new coins but since I only have 2 gpu right now I 'm staying away from coins _sp offering mods for

Did you use Alexis78 ccminer/where do you mine? It totally rocks with around 210W at wall for each card and 4.6-4.9MH/W. It's stable 970mh on my cards, one day I've got less than 680 on The Block Factory.
Did someone succeeded to set up skein solo mining? Got some nice block count on pool ^^

Guys I've been mining DGB skein for almost 2 months with 2xGPU rig, cashout yesterday for some nice profit but those difficulty increase yesterday with so many miners hopping into dgb killed my 800+ coins daily to ~500 :x Someone can share any algo similar to skein in term of 1080ti dominance? My Gigabyte GAMING X were at ~54 Celsius at 60% fan with 75%tdp.
I've been following this thread from beginning, thanks everyone for sharing insights, learned a lot from You guys:)

Hi, POPPY seems to be a very promising project, I definitely could imagine tieing it to agriculture for use sakes if it'd ever been an issue.
For now I've thrown 70MH into a network and running staking node. Looking forward to see any development plan schedule or something that could bring investors when full POS kicks in
Fingers crossed