Thanks @dmitry-buterin for the reply and this is what I have so far.

    Expected earnings in both Ether and Dollars. The calculations are based on the assumption that all conditions (difficulty and prices) remain as they are below.

    Enter your hash rate (MH/s) 25
    Power consumption (in Watts) 125
    Cost per KW/h ($) 0.13

    Network HashRate (GH/s) 17,345.01
    Average Block Time (Secs) 14.48
    Price of 1 Ether (USD) $42.73

    Calculated Mining Earnings :

    Duration * Ether Earned * Power Cost * Profit

    Per Hour * 0.00179171692990078 ($0.0766) * $0.0163 * $0.0603
    Per Day * 0.0430012063176188 ($1.8374) * $0.3900 * $1.4474
    Per Week * 0.301008444223331 ($12.8621) * $2.7300 * $10.1321
    Per Month * 1.29003618952856 ($55.1232) * $11.7000 * $43.4232

    Edited on April 07, 2017
    This is what I’m looking to mine with and calculated Total Investment Cost:

    Motherboard:
    ASRock Z97 Anniversary LGA 1150 Motherboard / $110

    Graphics cards:
    XFX RX-480 AMD Radeon GTR 8GB / $210 * 6 = $1260

    Power Supply:
    EVGA SuperNOVA 1000 G1, 80+ GOLD 1000W, 5 Year Warranty / $140

    RAM:
    Kingston Value RAM 4GB 1600MHz / $24

    Hard Drive:
    SanDisk SSD PLUS 120GB Solid State Drive / $50

    Riser Cable:
    DN Powered Riser Cable 16X PCI-E PCI-Express / $8

    Total investment cost for building ethereum mining rig = $1,592

    any suggesting (feedback) would be great
    Thanks for your time

    So what was the outcome of your calculation – earnings per month?
    Difficulty will keep increasing, that’s a given. So look at the prev 12 month and extrapolate.
    Have you look into Genesis mining? If I read their pricing right, they offer 30MH/s for $869 for 2 years, this seems to make more sense than your own rig for $1600 if you expect 25MH/s
    Wow I totally only cal for one GPU at 25MH/s so it should be 150M/H/s (6 GPU) in the above mining calculation.

    So with that being said that
    Per Month: 7.83467206021827 ($329.3696) ETH
    Power Cost: $11.7000 per Month
    Profit: $317.6696 per Month

    so that 93.6 ETH a year (give or take)
    In 4 month the rig will be paid for and the rest is profit

    Thanks so much again for your input and yes I looked into Genesis mining but wasn’t interested in working with them (but they do have a nice setup 🙂

    FYI
    I’m using this calculator if anyone wanted to know
    etherscan.io/ether-mining-calculator/

    As a comparison I have a 5TH bitcoin contract with Genesis and I get about .0014 BTC/day which is currently between $1.50-$1.75 per day. It is a lifetime contract which means it never expires but I must pay maintenance fees which cover equip/power/etc. The maintenance fees are $.28 per TH/s per day which are subtracted each day before I get my daily payout so basically I get about 50% of the BTC value generated each day as long as the amount earned does covers the maintenance fees for the prior 60 days. If the price of BTC goes down or the difficulty increases which is guaranteed to occur, the amount received is lower and eventually after 60 days with no payments to me it would be terminated by Genesis. I’ve had the contract for about 2 months now and it costed $670 so it will take about 450 days to earn my original investment back at this pace. It is a gamble that the price of BTC will continue to rise and that the difficulty doesn’t increase so much during this time to kill my investment. But then again all of the coins, both BTC and alt coins, are risks so must be considered with a hefty grain of salt.