I have 2 R9 290s,mining grin one does 2.5Gps, another does 2.77, I'll be trying to figure that out later. It's lower power than eth, but I'm not sure by how much as my kill-a-watt is dead. It will work on linux (tested with SMOS myself), it might work on windows 7, but not windows 10. On Linux you can get 27-31MH/s on ethash (vs the 20-24 on windows) too. My experience mining cryptonight variants on my 290s has been.. well I'm only getting 700 or so H/s. Grin was definitely making me more profit, and eth classic making the most revenue and maybe profit. You need to use Hawaii Bios Editor to do any overclocking/undervolting you want if using them on linux.
edit: lolminer is miner to use for grin on AMD.
edit2: Less typical or efficient algos the 290s can do are: the equihash variants, like zhash, BEAM, and I believe Aion but I didn't test that one myself. I believe mine were outperforming my RX 580 on BEAM, too, but I've only tested on linux. Windows 7 may work the same even though it doesn't get the memory management benefits of linux, where the ethash performance difference comes from. They can do the C31 algo, for grin, as well with lolminer but only at .27 gps, though they ran fairly cool when mining that so power efficiency may be better there.

no body know when the real bull will coming back to cryptocurrencies
but, personally i still believe if in the future bitcoin and altcoins price will growing, even touch the new high level my friend

actually I was tired of holding on to holding these tokens and coins, which used to be very high now with a very unstable market condition, I was still excited to wait for the market to return to green

I also beleive its going to come back with a vengeance. Now everything is on amazing discount. Buying BTC when it hits the bottom is a no brainer for me. BTC is the safest bet probably as it will always be a store of value. As for GPU mining, if you believe that it will have a comeback then its good time to buy used GPUs. Otherwise don't. FGPA started to seriously affect the mining. Although I did not expect them to.

Save our coins with a long time sometimes makes us bored and want to sell it, but believe me, if the coin is a potential then hold it is the best solution for long-term investment, because potential coins are always there will add new features in the future which make the price going up. 

Many say patience is the key to success, but we also need to cultivate if the good opportunity comes then just take it, then using patience and good opportunities is wiser. Hold the coins we have until the opportunity is good and take action to get a profit.

280, damn thats vintage
With current prices there is no stable coin that would return you instant profit.

Now it is worth buying ETH and keeping coins until the end of the year.  Or you can try some of the money to invest in EOS.

Invest now in EOS.  It is very likely that in two years this coin will be as popular as ETH.

Invest now in ETH and as the market recovers you can easily make a profit.  Now this is the best option.

The best alt coins that i can think of are probably Ripple, Litecoin, Ethereum, and Monero.  Also now that the market has fallen off a little bit its a great opportunity to join in and start increasing your stock pile of coins. 

I would advise you to invest in EOS because this coin has a good potential and the EOS network was recently launched.  I think this coin will continue to develop.

So far infrastructure coins were the best investments. EOS, Icon and lately my personal favourite Zilliqa (which is the best one out there nowadays IMO). However, today you can find a project which promises 1M tsp in every corner... time to move on and focus on real projects, blokchain infrastructure is getting ready soon (wait for 2nd 3rd generation blockchain to release mainnet).

Ethereum always had two big problems: Governance and Turing-completeness.  I would put my money on XCP instead.

Of cource, or how he test their product in real conditions
Its like the engineering samples of cpu's by intel, this type of machines bitmain will leave for himself

No Bitmain is definitely not mining Ethereum. if they had developed an ASIC then it would be already on sale right now.

I am also running a few 7970 aka 280x, @1050/1400 1110-1150mV (depends on the specific card) and making with a modded BIOS ~300+ Sol per card. If the -i setting does nothing, then something is wrong on your side, mine 280x' run stable with i 4.

I think ETH will have a big growth in 2018 , because so many good tokens/coins are based on ethereums ERC20.

Yes, all electronic coin in the market is worthy to buy since they will provides you lots of income. You will just learn to wait because investing is very a long process to consider just to have a huge income.