Grain Steeping and Water Usage (extract brewer)

So what effect does the water used to steep the grains in, have on the overall finished product?  Some recipes say to steep in 2 gallons of water.  Others 3.  Some recipes say to steep at 170 degree water for 30 mins, others say to place grains in cool water and slowly heat to 170, then remove the grains.  All things being the same, will the steps above produce the same beer or will the beer have a different characteristic?

I may be an extract brewer, but I do have a larger sized pot (30L).  I've been told it's better to boil as much of the entire 5 gallons as I can.  So if I steep in 2 gallons of water, then add extract/hops/etc and water to make 5 gallons, will that affect anything?

So many variables here.  Is it really that important?  Or am I being too OCD?

If I had to guess, I'd say no it is not important because we top off our fermenter with water till we reach 5 gallons. 

But I don't know.  Thoughts anyone?

Thanks!

I'm an extract brewer as well (hopefully I'll graduate to whole grain soon) and I've done all 5 gallon boils. I have an 8 gallon brew kettle, my beers have come out great so far.

Not a pro by any means but after 60 gallons of extract beers so far I can offer you this: We generally steep in 3 gallons at 155 degrees for 30 minutes, top off the pot to 6.25 gallons and begin the boil process, we lose about 1-1.15 gallons in boil off so we wind up with about 5-5.25 gallons of wort. All of our gravities have been pretty spot on and all our beers have been exceptional! Now we are taking the next step and starting to do mini mash/partial mash and those are turning out great as well. Someone told me a while back-drink the beer, not the numbers, it is far from an exact science and if you like your beer that's all that matters!
Cheers!