I would use
EcuTunerGuy, he's affordable (no middle man) and has tuned both my ka-t powered cars (s13 and Datsun 240z) my ka24de n/a, my infiniti q45 with ethanol and gas tune with 150 shot of nos, my subaru wrx, and my rb26det build (he wired it and tuned it to run with an rb20det ecu.
I haven't had issues with his tuning ability, hes a genius with math and programming! blows my mind!!! he's local in San Diego area, but also will talk to you on the phone before shipping out your product and will retune if you change setups or run into trouble with very quick turn-around.
Like everyone is saying, i would stick with a stock ecu and just have it chipped and tuned. the stock tune is good for stock, but when you want any mods done you need to change the timing and fuel maps to make it run properly, just like the stock computer runs stock so well! the stuck ecu is amazing and is sufficiant for almost any modification and can be programmed to run just about any maf, injector size, turbo, launch control, and you can go back to stock or have multiple tunes and change them, at any time.... stand alone is not necessary unless you are starting with a non-tunable ecu or no parameters like: like add vvt sr20 or rb25 head and fuctionality on a non-vvt engine with non vvt ecu.