If you have enough capacity, go with boiling the full volume, use a chiller, and adjust hops (downward - save $) - it just makes better beer, on average. Good beer can be made either way, of course. May also help slide you toward the all-grain slippery slope.
Of course, depending on your pot size you may want to start with more than 5 gallons, so that you end up with about 5 after boiling off some - but if you are starting with 5 gallons of water and adding extract to it, you'll be over 5 gallons to start anyway.
Re-filling the pipeline - got a lot of brewing to do.