well you sound like a pretty serious trader then and probably need something better than iress, especially seems your trading off the 1 minute charts.
doubt iress would be much good to ya because you really need 10 plus days of historic intraday data to find s and r on the intraday charts to be able to make educated trading decisions, its useless only supplying the current day... unless you find staring at about 10 candlesticks interesting :S
Spark in my view is way to expensive, never used it before so unsure of charting, I think they more specialize in market depth analysis etc. That seems to be their proprietary selling point.
It all really comes down to what your willing to pay. You could pay to get paritech pulse or bourse data or spark for like $150 -200 a month or my preferred option, sign up with IG markets and get an asx live feed for only $37 bucks a month
which they use the IT finance charts. Some people say their data isnt that accurate which it probably isnt as I have found a few times its incorrect but its pretty good.
OR another option, get an etrade account and use etrade pro, NOT power etrade as that is just the useless IRESS. Etrade pro is good because you can see intraday data on about 5 or 6 different time frames and is the same price as IRESS per month ($80)