Having the plumbing for the washing machine is a nice benefit, since you can split off of it and have a convenient water source and drain.
a couple 10 gallons seems kinda small, if whoever is cool with you partially adapting the laundry room to a fish room, maybe see if you can put in a couple of bigger tanks.
Maybe a 2-3 level stand, with big tanks (like a 40B, etc.) on the bottom, and smaller (29's, 10's, etc.) above.
If you aren't terribly concerned with making it pretty, cheap and strong stands are pretty easy to do w/ 2x4s