Making a 3 gal wort and topping with 2 gal boiled water; difference in taste?

So I'm looking at boiling pots for my 5 gal system. I've read you can boil 2 gallons ahead of time (like the night before) and let it cool, and boil 3.5 gallons for the wort at brew time. Then use the 2 gallons to help cool the wort down when done to bring the total volume up to 5 gallons total.

Is there any difference in taste with this method since the hops don't steep in all of the water? Would you get better taste by doing it all at once?

My Mom has a 21.5 quart canning pot that is free for me to use (good since I've spend lots of $ so far getting everything together). I'd have to only boil the 3.5 gal in it, but if the taste is going to suffer, I'll consider getting a larger one instead.

Thanks,
Steve

I'm led to believe that boiling the whole wort is better, but you can definitely brew fine with a smaller wort.

My first brew was from a kit that had me make 1-1.5 gallons of wort and then add enough water to that to bring it up to 5 gallons. I haven't had a chance to taste it yet but it certainly isn't short of colour and odor... it's very dark and very hoppy. =)

I use a 5 gallon Rubbermaid cooler and 6 gallon turkey fryer pots. They are a bit small for 5 gallon batches but it works. On Brew day I often boil up an extra gallon or two of water in a covered pot and I set it in plastic tote full of ice water to cool. If I miss my volume I top off the fermentor with my sterilized & cooled water. You can boil the extra water the night before but I am hesitant about letting it go too long between sterilizing and use. Even if you leave the lid on as the pot cools the air inside will contract and draw air in around the lid so there is a very, very minor possibility of contamination. But even if the water is contaminated there is nothing for any bacteria or wild yeasts to eat so their numbers should be very low and your brewing yeast should easily kick their butt.

What you are talking about is doing a "partial boil", and then "topping off".

Partial boils are fine, and many brewers with limited space (such as myself) and on electric stoves (such as myself) do them often. If the recipe calls for a full boil, then you may need to adjust your hops slightly (beer calculus at www.hopville.com can help with that).

Other than that, do a search for the terms above, or go to the HBT WIKi - tons of information there that often gets overlooked.